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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0703044 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | de Sitter space and the equivalence between f(R) and scalar-tensor
gravity | 4 pages, revtex, to appear in Phys. Rev. D. Revised version contains
additional and updated references | Phys.Rev.D75:067302,2007 | 10.1103/PhysRevD.75.067302 | null | gr-qc | null | It is shown that, when f'' is non-vanishing, metric f(R) gravity is
completely equivalent to a scalar-tensor theory (with zero Brans-Dicke
parameter) with respect to perturbations of de Sitter space, contrary to
previous expectations. Moreover, the stability conditions of de Sitter space
with respect to homogeneous and inhomogeneous perturbations coincide in most
scalar-tensor theories, as is the case in metric f(R) gravity.
| [
{
"created": "Tue, 6 Mar 2007 23:23:21 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Mar 2007 13:41:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | It is shown that, when f'' is non-vanishing, metric f(R) gravity is completely equivalent to a scalar-tensor theory (with zero Brans-Dicke parameter) with respect to perturbations of de Sitter space, contrary to previous expectations. Moreover, the stability conditions of de Sitter space with respect to homogeneous and inhomogeneous perturbations coincide in most scalar-tensor theories, as is the case in metric f(R) gravity. |
0810.4152 | Sean Gryb B | Sean B. Gryb | Quantum Machian Time in Toy Models of Gravity | 27 pages, references added, typos fixed, additional comments added to
abs/intro/concl, journal ref added | Class.Quant.Grav.26:085015,2009 | 10.1088/0264-9381/26/8/085015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity on closed spatial topologies can be derived, using a
technique called "best-matching", as an evolving 3-geometry subject to
constraints. These constraints can be thought of as a way of imposing temporal
and spatial relationalism. The same type of constraints can be used in
non-relativistic particle models to produce relational theories that suffer
from the same Problem of Time as that encountered in General Relativity. As a
result, these simple toy models are well suited for studying the Problem of
Time in quantum gravity. In this paper, a version of these particle models is
studied where we "best-match" the time translational invariance of the theory.
Using insights gained from this procedure, we can move back and forth between
absolute and relational time by changing the way in which the relational fields
are varied. We then proceed to quantize this theory using Dirac and path
integral quantizations. We discover that one of the constraints of the theory,
which we call the Mach constraint, is responsible for removing the dependence
of the theory on a background structure. It is this Mach constraint that is
responsible for making the theory temporally relational. Because of the deep
relationship between these models and General Relativity, this work may shed
new light on the Problem of Time in quantum gravity and how one might expect
time to emerge on quantum subsystems of the universe.
| [
{
"created": "Wed, 22 Oct 2008 20:17:15 GMT",
"version": "v1"
},
{
"created": "Wed, 6 May 2009 19:24:01 GMT",
"version": "v2"
}
] | 2009-11-18 | [
[
"Gryb",
"Sean B.",
""
]
] | General Relativity on closed spatial topologies can be derived, using a technique called "best-matching", as an evolving 3-geometry subject to constraints. These constraints can be thought of as a way of imposing temporal and spatial relationalism. The same type of constraints can be used in non-relativistic particle models to produce relational theories that suffer from the same Problem of Time as that encountered in General Relativity. As a result, these simple toy models are well suited for studying the Problem of Time in quantum gravity. In this paper, a version of these particle models is studied where we "best-match" the time translational invariance of the theory. Using insights gained from this procedure, we can move back and forth between absolute and relational time by changing the way in which the relational fields are varied. We then proceed to quantize this theory using Dirac and path integral quantizations. We discover that one of the constraints of the theory, which we call the Mach constraint, is responsible for removing the dependence of the theory on a background structure. It is this Mach constraint that is responsible for making the theory temporally relational. Because of the deep relationship between these models and General Relativity, this work may shed new light on the Problem of Time in quantum gravity and how one might expect time to emerge on quantum subsystems of the universe. |
2202.06092 | Ali Banijamali | Behnaz Fazlpour, Ali Banijamali, Valerio Faraoni | Geometry of static $w=-1/5$ perfect fluid spheres in general relativity | 8 pages, latex | null | 10.1140/epjc/s10052-022-10349-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the physical features of two recent classes of analytical
solutions of the Einstein equations sourced by an exotic perfect fluid with
equation of state $ P=-\rho/5$. These geometries depend on up to four
parameters and are static and spherically symmetric. They describe compact
spaces with naked central singularities.
| [
{
"created": "Sat, 12 Feb 2022 16:07:16 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Apr 2022 05:56:21 GMT",
"version": "v2"
}
] | 2022-05-11 | [
[
"Fazlpour",
"Behnaz",
""
],
[
"Banijamali",
"Ali",
""
],
[
"Faraoni",
"Valerio",
""
]
] | We discuss the physical features of two recent classes of analytical solutions of the Einstein equations sourced by an exotic perfect fluid with equation of state $ P=-\rho/5$. These geometries depend on up to four parameters and are static and spherically symmetric. They describe compact spaces with naked central singularities. |
2311.03718 | Mikko Laine | H. Kolesova, M. Laine | Update on gravitational wave signals from post-inflationary phase
transitions | 12 pages. v2: minor fixes and clarifications | Phys.Lett.B 851 (2024) 138553 | 10.1016/j.physletb.2024.138553 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In view of recent interest in high-frequency detectors, broad features of
gravitational wave signals from phase transitions taking place soon after
inflation are summarized. The influence of the matter domination era that
follows the slow-roll stage is quantified in terms of two equilibration rates.
Turning to the highest-frequency part of the spectrum, we show how it is
constrained by the fact that the bubble distance scale must exceed the mean
free path.
| [
{
"created": "Tue, 7 Nov 2023 04:52:07 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Mar 2024 10:05:57 GMT",
"version": "v2"
}
] | 2024-03-14 | [
[
"Kolesova",
"H.",
""
],
[
"Laine",
"M.",
""
]
] | In view of recent interest in high-frequency detectors, broad features of gravitational wave signals from phase transitions taking place soon after inflation are summarized. The influence of the matter domination era that follows the slow-roll stage is quantified in terms of two equilibration rates. Turning to the highest-frequency part of the spectrum, we show how it is constrained by the fact that the bubble distance scale must exceed the mean free path. |
0808.1745 | Christopher Beetle | Christopher Beetle | Approximate Killing Fields as an Eigenvalue Problem | 4 pages, RevTeX | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Approximate Killing vector fields are expected to help define physically
meaningful spins for non-symmetric black holes in general relativity. However,
it is not obvious how such fields should be defined geometrically. This paper
relates a definition suggested recently by Cook and Whiting to an older
proposal by Matzner, which seems to have been overlooked in the recent
literature. It also describes how to calculate approximate Killing fields based
on these proposals using an efficient scheme that could be of immediate
practical use in numerical relativity.
| [
{
"created": "Tue, 12 Aug 2008 22:16:38 GMT",
"version": "v1"
}
] | 2008-08-14 | [
[
"Beetle",
"Christopher",
""
]
] | Approximate Killing vector fields are expected to help define physically meaningful spins for non-symmetric black holes in general relativity. However, it is not obvious how such fields should be defined geometrically. This paper relates a definition suggested recently by Cook and Whiting to an older proposal by Matzner, which seems to have been overlooked in the recent literature. It also describes how to calculate approximate Killing fields based on these proposals using an efficient scheme that could be of immediate practical use in numerical relativity. |
2209.13277 | Guillaume Boileau | Guillaume Boileau and Nelson Christensen and Chloe Gowling and Mark
Hindmarsh and Renate Meyer | Prospects for LISA to detect a gravitational-wave background from first
order phase transitions | null | JCAP02(2023)056 | 10.1088/1475-7516/2023/02/056 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First order phase transitions in the early universe could produce a
gravitational-wave background that might be detectable by the Laser
Interferometer Space Antenna (LISA). Such an observation would provide evidence
for physics beyond the Standard Model. We study the ability of LISA to observe
a gravitational-wave background from phase transitions in the presence of an
extragalactic foreground from binary black hole mergers throughout the
universe, a galactic foreground from white dwarf binaries, and LISA noise.
Modelling the phase transition gravitational wave background as a double broken
power law, we use the deviance information criterion as a detection statistic,
and Fisher matrix and Markov Chain Monte Carlo methods to assess the
measurement accuracy of the parameters of the power spectrum. While estimating
all the parameters associated with the gravitational-wave backgrounds,
foregrounds, and LISA noise, we find that LISA could detect a
gravitational-wave background from phase transitions with a peak frequency of 1
mHz and normalized energy density amplitude of $\Omega_{\text p} \simeq 3
\times 10^{-11}$. With $\Omega_{\text p} \simeq 10^{-10}$, the signal is
detectable if the peak frequency is in the range $4 \times 10^{-4}$ to $9
\times 10^{-3}$ Hz, and the peak amplitude and frequency can be estimated to an
accuracy of 10\% to 1\%.
| [
{
"created": "Tue, 27 Sep 2022 09:50:51 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2023 17:04:24 GMT",
"version": "v2"
}
] | 2023-03-01 | [
[
"Boileau",
"Guillaume",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Gowling",
"Chloe",
""
],
[
"Hindmarsh",
"Mark",
""
],
[
"Meyer",
"Renate",
""
]
] | First order phase transitions in the early universe could produce a gravitational-wave background that might be detectable by the Laser Interferometer Space Antenna (LISA). Such an observation would provide evidence for physics beyond the Standard Model. We study the ability of LISA to observe a gravitational-wave background from phase transitions in the presence of an extragalactic foreground from binary black hole mergers throughout the universe, a galactic foreground from white dwarf binaries, and LISA noise. Modelling the phase transition gravitational wave background as a double broken power law, we use the deviance information criterion as a detection statistic, and Fisher matrix and Markov Chain Monte Carlo methods to assess the measurement accuracy of the parameters of the power spectrum. While estimating all the parameters associated with the gravitational-wave backgrounds, foregrounds, and LISA noise, we find that LISA could detect a gravitational-wave background from phase transitions with a peak frequency of 1 mHz and normalized energy density amplitude of $\Omega_{\text p} \simeq 3 \times 10^{-11}$. With $\Omega_{\text p} \simeq 10^{-10}$, the signal is detectable if the peak frequency is in the range $4 \times 10^{-4}$ to $9 \times 10^{-3}$ Hz, and the peak amplitude and frequency can be estimated to an accuracy of 10\% to 1\%. |
gr-qc/0506037 | Carsten Gundlach | Carsten Gundlach and Jose M. Martin-Garcia | Hyperbolicity of second-order in space systems of evolution equations | null | Class.Quant.Grav. 23 (2006) S387-S404 | 10.1088/0264-9381/23/16/S06 | null | gr-qc | null | A possible definition of strong/symmetric hyperbolicity for a second-order
system of evolution equations is that it admits a reduction to first order
which is strongly/symmetric hyperbolic. We investigate the general system that
admits a reduction to first order and give necessary and sufficient criteria
for strong/symmetric hyperbolicity of the reduction in terms of the principal
part of the original second-order system. An alternative definition of strong
hyperbolicity is based on the existence of a complete set of characteristic
variables, and an alternative definition of symmetric hyperbolicity is based on
the existence of a conserved (up to lower order terms) energy. Both these
definitions are made without any explicit reduction. Finally, strong
hyperbolicity can be defined through a pseudo-differential reduction to first
order. We prove that both definitions of symmetric hyperbolicity are equivalent
and that all three definitions of strong hyperbolicity are equivalent (in three
space dimensions). We show how to impose maximally dissipative boundary
conditions on any symmetric hyperbolic second order system. We prove that if
the second-order system is strongly hyperbolic, any closed constraint evolution
system associated with it is also strongly hyperbolic, and that the
characteristic variables of the constraint system are derivatives of a subset
of the characteristic variables of the main system, with the same speeds.
| [
{
"created": "Mon, 6 Jun 2005 17:39:23 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gundlach",
"Carsten",
""
],
[
"Martin-Garcia",
"Jose M.",
""
]
] | A possible definition of strong/symmetric hyperbolicity for a second-order system of evolution equations is that it admits a reduction to first order which is strongly/symmetric hyperbolic. We investigate the general system that admits a reduction to first order and give necessary and sufficient criteria for strong/symmetric hyperbolicity of the reduction in terms of the principal part of the original second-order system. An alternative definition of strong hyperbolicity is based on the existence of a complete set of characteristic variables, and an alternative definition of symmetric hyperbolicity is based on the existence of a conserved (up to lower order terms) energy. Both these definitions are made without any explicit reduction. Finally, strong hyperbolicity can be defined through a pseudo-differential reduction to first order. We prove that both definitions of symmetric hyperbolicity are equivalent and that all three definitions of strong hyperbolicity are equivalent (in three space dimensions). We show how to impose maximally dissipative boundary conditions on any symmetric hyperbolic second order system. We prove that if the second-order system is strongly hyperbolic, any closed constraint evolution system associated with it is also strongly hyperbolic, and that the characteristic variables of the constraint system are derivatives of a subset of the characteristic variables of the main system, with the same speeds. |
gr-qc/9612062 | Olaf Lechtenfeld | Helge Dennhardt, Olaf Lechtenfeld (Univ. of Hannover, Germany) | Scalar Deformations of Schwarzschild Holes and Their Stability | 24 pp, 16 figs, Latex; version published in Int. J. Mod. Phys. A | Int.J.Mod.Phys. A13 (1998) 741-764 | 10.1142/S0217751X98000329 | IASSNS-HEP-96/130 and ITP-UH-28/96 | gr-qc hep-th | null | We construct two solutions of the minimally coupled Einstein-scalar field
equations, representing regular deformations of Schwarzschild black holes by a
self-interacting, static, scalar field. One solution features an exponentially
decaying scalar field and a triple-well interaction potential; the other one is
completely analytic and sprouts Coulomb-like scalar hair. Both evade the
no-hair theorem by having partially negative potential, in conflict with the
dominant energy condition. The linear perturbation theory around such
backgrounds is developed in general, and yields stability criteria in terms of
effective potentials for an analog Schr\"odinger problem. We can test for more
than half of the perturbation modes, and our solutions prove to be stable
against those.
| [
{
"created": "Sat, 21 Dec 1996 01:44:46 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jan 1998 15:16:06 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Dennhardt",
"Helge",
"",
"Univ. of Hannover, Germany"
],
[
"Lechtenfeld",
"Olaf",
"",
"Univ. of Hannover, Germany"
]
] | We construct two solutions of the minimally coupled Einstein-scalar field equations, representing regular deformations of Schwarzschild black holes by a self-interacting, static, scalar field. One solution features an exponentially decaying scalar field and a triple-well interaction potential; the other one is completely analytic and sprouts Coulomb-like scalar hair. Both evade the no-hair theorem by having partially negative potential, in conflict with the dominant energy condition. The linear perturbation theory around such backgrounds is developed in general, and yields stability criteria in terms of effective potentials for an analog Schr\"odinger problem. We can test for more than half of the perturbation modes, and our solutions prove to be stable against those. |
1112.5004 | Emma Robinson | J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T.
Accadia, F. Acernese, C. Adams, R. Adhikari, C. Affeldt, M. Agathos, K.
Agatsuma, P. Ajith, B. Allen, E. Amador Ceron, D. Amariutei, S. B. Anderson,
W. G. Anderson, K. Arai, M. A. Arain, M. C. Araya, S. M. Aston, P. Astone, D.
Atkinson, P. Aufmuth, C. Aulbert, B. E. Aylott, S. Babak, P. Baker, G.
Ballardin, S. Ballmer, J. C. B. Barayoga, D. Barker, F. Barone, B. Barr, L.
Barsotti, M. Barsuglia, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika,
A. Basti, J. Batch, J. Bauchrowitz, Th. S. Bauer, M. Bebronne, D. Beck, B.
Behnke, M. Bejger, M.G. Beker, A. S. Bell, A. Belletoile, I. Belopolski, M.
Benacquista, J. M. Berliner, A. Bertolini, J. Betzwieser, N. Beveridge, P. T.
Beyersdorf, I. A. Bilenko, G. Billingsley, J. Birch, R. Biswas, M. Bitossi,
M. A. Bizouard, E. Black, J. K. Blackburn, L. Blackburn, D. Blair, B. Bland,
M. Blom, O. Bock, T. P. Bodiya, C. Bogan, R. Bondarescu, F. Bondu, L.
Bonelli, R. Bonnand, R. Bork, M. Born, V. Boschi, S. Bose, L. Bosi, B.
Bouhou, S. Braccini, C. Bradaschia, P. R. Brady, V. B. Braginsky, M.
Branchesi, J. E. Brau, J. Breyer, T. Briant, D. O. Bridges, A. Brillet, M.
Brinkmann, V. Brisson, M. Britzger, A. F. Brooks, D. A. Brown, T. Bulik, H.
J. Bulten, A. Buonanno, J. Burguet--Castell, D. Buskulic, C. Buy, R. L. Byer,
L. Cadonati, G. Cagnoli, E. Calloni, J. B. Camp, P. Campsie, J. Cannizzo, K.
Cannon, B. Canuel, J. Cao, C. D. Capano, F. Carbognani, L. Carbone, S.
Caride, S. Caudill, M. Cavagli\`a, F. Cavalier, R. Cavalieri, G. Cella, C.
Cepeda, E. Cesarini, O. Chaibi, T. Chalermsongsak, P. Charlton, E.
Chassande-Mottin, S. Chelkowski, W. Chen, X. Chen, Y. Chen, A. Chincarini, A.
Chiummo, H. Cho, J. Chow, N. Christensen, S. S. Y. Chua, C. T. Y. Chung, S.
Chung, G. Ciani, D. E. Clark, J. Clark, J. H. Clayton, F. Cleva, E. Coccia,
P.-F. Cohadon, C. N. Colacino, J. Colas, A. Colla, M. Colombini, A. Conte, R.
Conte, D. Cook, T. R. Corbitt, M. Cordier, N. Cornish, A. Corsi, C. A. Costa,
M. Coughlin, J.-P. Coulon, P. Couvares, D. M. Coward, M. Cowart, D. C. Coyne,
J. D. E. Creighton, T. D. Creighton, A. M. Cruise, A. Cumming, L. Cunningham,
E. Cuoco, R. M. Cutler, K. Dahl, S. L. Danilishin, R. Dannenberg, S.
D'Antonio, K. Danzmann, V. Dattilo, B. Daudert, H. Daveloza, M. Davier, E. J.
Daw, R. Day, T. Dayanga, R. De Rosa, D. DeBra, G. Debreczeni, W. Del Pozzo,
M. del Prete, T. Dent, V. Dergachev, R. DeRosa, R. DeSalvo, S. Dhurandhar, L.
Di Fiore, A. Di Lieto, I. Di Palma, M. Di Paolo Emilio, A. Di Virgilio, M.
D\'iaz, A. Dietz, F. Donovan, K. L. Dooley, M. Drago, R. W. P. Drever, J. C.
Driggers, Z. Du, J.-C. Dumas, T. Eberle, M. Edgar, M. Edwards, A. Effler, P.
Ehrens, G. Endr\H{o}czi, R. Engel, T. Etzel, K. Evans, M. Evans, T. Evans, M.
Factourovich, V. Fafone, S. Fairhurst, Y. Fan, B. F. Farr, D. Fazi, H.
Fehrmann, D. Feldbaum, F. Feroz, I. Ferrante, F. Fidecaro, L. S. Finn, I.
Fiori, R. P. Fisher, R. Flaminio, M. Flanigan, S. Foley, E. Forsi, L. A.
Forte, N. Fotopoulos, J.-D. Fournier, J. Franc, S. Frasca, F. Frasconi, M.
Frede, M. Frei, Z. Frei, A. Freise, R. Frey, T. T. Fricke, D. Friedrich, P.
Fritschel, V. V. Frolov, M.-K. Fujimoto, P. J. Fulda, M. Fyffe, J. Gair, M.
Galimberti, L. Gammaitoni, J. Garcia, F. Garufi, M. E. G\'asp\'ar, G. Gemme,
R. Geng, E. Genin, A. Gennai, L. \'A. Gergely, S. Ghosh, J. A. Giaime, S.
Giampanis, K. D. Giardina, A. Giazotto, S. Gil, C. Gill, J. Gleason, E.
Goetz, L. M. Goggin, G. Gonz\'alez, M. L. Gorodetsky, S. Go{\ss}ler, R.
Gouaty, C. Graef, P. B. Graff, M. Granata, A. Grant, S. Gras, C. Gray, N.
Gray, R. J. S. Greenhalgh, A. M. Gretarsson, C. Greverie, R. Grosso, H.
Grote, S. Grunewald, G. M. Guidi, R. Gupta, E. K. Gustafson, R. Gustafson, T.
Ha, J. M. Hallam, D. Hammer, G. Hammond, J. Hanks, C. Hanna, J. Hanson, J.
Harms, G. M. Harry, I. W. Harry, E. D. Harstad, M. T. Hartman, K. Haughian,
K. Hayama, J.-F. Hayau, J. Heefner, A. Heidmann, M. C. Heintze, H. Heitmann,
P. Hello, M. A. Hendry, I. S. Heng, A. W. Heptonstall, V. Herrera, M.
Hewitson, S. Hild, D. Hoak, K. A. Hodge, K. Holt, M. Holtrop, T. Hong, S.
Hooper, D. J. Hosken, J. Hough, E. J. Howell, B. Hughey, S. Husa, S. H.
Huttner, R. Inta, T. Isogai, A. Ivanov, K. Izumi, M. Jacobson, E. James, Y.
J. Jang, P. Jaranowski, E. Jesse, W. W. Johnson, D. I. Jones, G. Jones, R.
Jones, L. Ju, P. Kalmus, V. Kalogera, S. Kandhasamy, G. Kang, J. B. Kanner,
R. Kasturi, E. Katsavounidis, W. Katzman, H. Kaufer, K. Kawabe, S. Kawamura,
F. Kawazoe, D. Kelley, W. Kells, D. G. Keppel, Z. Keresztes, A. Khalaidovski,
F. Y. Khalili, E. A. Khazanov, B. Kim, C. Kim, H. Kim, K. Kim, N. Kim, Y. -M.
Kim, P. J. King, D. L. Kinzel, J. S. Kissel, S. Klimenko, K. Kokeyama, V.
Kondrashov, S. Koranda, W. Z. Korth, I. Kowalska, D. Kozak, O. Kranz, V.
Kringel, S. Krishnamurthy, B. Krishnan, A. Kr\'olak, G. Kuehn, R. Kumar, P.
Kwee, P. K. Lam, M. Landry, B. Lantz, N. Lastzka, C. Lawrie, A. Lazzarini, P.
Leaci, C. H. Lee, H. K. Lee, H. M. Lee, J. R. Leong, I. Leonor, N. Leroy, N.
Letendre, J. Li, T. G. F. Li, N. Liguori, P. E. Lindquist, Y. Liu, Z. Liu, N.
A. Lockerbie, D. Lodhia, M. Lorenzini, V. Loriette, M. Lormand, G. Losurdo,
J. Lough, J. Luan, M. Lubinski, H. L\"uck, A. P. Lundgren, E. Macdonald, B.
Machenschalk, M. MacInnis, D. M. Macleod, M. Mageswaran, K. Mailand, E.
Majorana, I. Maksimovic, N. Man, I. Mandel, V. Mandic, M. Mantovani, A.
Marandi, F. Marchesoni, F. Marion, S. M\'arka, Z. M\'arka, A. Markosyan, E.
Maros, J. Marque, F. Martelli, I. W. Martin, R. M. Martin, J. N. Marx, K.
Mason, A. Masserot, F. Matichard, L. Matone, R. A. Matzner, N. Mavalvala, G.
Mazzolo, R. McCarthy, D. E. McClelland, S. C. McGuire, G. McIntyre, J.
McIver, D. J. A. McKechan, S. McWilliams, G. D. Meadors, M. Mehmet, T. Meier,
A. Melatos, A. C. Melissinos, G. Mendell, R. A. Mercer, S. Meshkov, C.
Messenger, M. S. Meyer, C. Michel, L. Milano, J. Miller, Y. Minenkov, V. P.
Mitrofanov, G. Mitselmakher, R. Mittleman, O. Miyakawa, B. Moe, M. Mohan, S.
D. Mohanty, S. R. P. Mohapatra, G. Moreno, N. Morgado, A. Morgia, T. Mori, S.
R. Morriss, S. Mosca, K. Mossavi, B. Mours, C. M. Mow--Lowry, C. L. Mueller,
G. Mueller, S. Mukherjee, A. Mullavey, H. M\"uller-Ebhardt, J. Munch, D.
Murphy, P. G. Murray, A. Mytidis, T. Nash, L. Naticchioni, V. Necula, J.
Nelson, G. Newton, T. Nguyen, A. Nishizawa, A. Nitz, F. Nocera, D. Nolting,
M. E. Normandin, L. Nuttall, E. Ochsner, J. O'Dell, E. Oelker, G. H. Ogin, J.
J. Oh, S. H. Oh, B. O'Reilly, R. O'Shaughnessy, C. Osthelder, C. D. Ott, D.
J. Ottaway, R. S. Ottens, H. Overmier, B. J. Owen, A. Page, G. Pagliaroli, L.
Palladino, C. Palomba, Y. Pan, C. Pankow, F. Paoletti, M. A. Papa, M. Parisi,
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Th\"uring, K. V. Tokmakov, C. Tomlinson, A. Toncelli, M. Tonelli, O. Torre,
C. Torres, C. I. Torrie, E. Tournefier, F. Travasso, G. Traylor, K. Tseng, D.
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S. van der Putten, A. A. van Veggel, S. Vass, M. Vasuth, R. Vaulin, M.
Vavoulidis, A. Vecchio, G. Vedovato, J. Veitch, P. J. Veitch, C. Veltkamp, D.
Verkindt, F. Vetrano, A. Vicer\'e, A. E. Villar, J.-Y. Vinet, S. Vitale, S.
Vitale, H. Vocca, C. Vorvick, S. P. Vyatchanin, A. Wade, L. Wade, M. Wade, S.
J. Waldman, L. Wallace, Y. Wan, M. Wang, X. Wang, Z. Wang, A. Wanner, R. L.
Ward, M. Was, M. Weinert, A. J. Weinstein, R. Weiss, L. Wen, P. Wessels, M.
West, T. Westphal, K. Wette, J. T. Whelan, S. E. Whitcomb, D. J. White, B. F.
Whiting, C. Wilkinson, P. A. Willems, L. Williams, R. Williams, B. Willke, L.
Winkelmann, W. Winkler, C. C. Wipf, A. G. Wiseman, H. Wittel, G. Woan, R.
Wooley, J. Worden, I. Yakushin, H. Yamamoto, K. Yamamoto, C. C. Yancey, H.
Yang, D. Yeaton-Massey, S. Yoshida, P. Yu, M. Yvert, A. Zadro\'zny, M.
Zanolin, J.-P. Zendri, F. Zhang, L. Zhang, W. Zhang, C. Zhao, N. Zotov, M. E.
Zucker, J. Zweizig | Upper limits on a stochastic gravitational-wave background using LIGO
and Virgo interferometers at 600-1000 Hz | 29 pages, 6 figures. For a repository of data used in the
publication, please see
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=22210. Also see the
announcement for this paper at
http://www.ligo.org/science/Publication-S5VSR1StochIso/ | null | 10.1103/PhysRevD.85.122001 | LIGO-P1000128-v22 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A stochastic background of gravitational waves is expected to arise from a
superposition of many incoherent sources of gravitational waves, of either
cosmological or astrophysical origin. This background is a target for the
current generation of ground-based detectors. In this article we present the
first joint search for a stochastic background using data from the LIGO and
Virgo interferometers. In a frequency band of 600-1000 Hz, we obtained a 95%
upper limit on the amplitude of $\Omega_{\rm GW}(f) = \Omega_3 (f/900
\mathrm{Hz})^3$, of $\Omega_3 < 0.33$, assuming a value of the Hubble parameter
of $h_{100}=0.72$. These new limits are a factor of seven better than the
previous best in this frequency band.
| [
{
"created": "Wed, 21 Dec 2011 12:15:48 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jan 2012 13:22:02 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Jan 2012 12:52:22 GMT",
"version": "v3"
},
{
"created": "Thu, 23 Feb 2012 19:05:58 GMT",
"version": "v4"
}
] | 2016-08-14 | [
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],
[
"Stone",
"R.",
""
],
[
"Strain",
"K. A.",
""
],
[
"Strigin",
"S. E.",
""
],
[
"Stroeer",
"A. S.",
""
],
[
"Sturani",
"R.",
""
],
[
"Stuver",
"A. L.",
""
],
[
"Summerscales",
"T. Z.",
""
],
[
"Sung",
"M.",
""
],
[
"Susmithan",
"S.",
""
],
[
"Sutton",
"P. J.",
""
],
[
"Swinkels",
"B.",
""
],
[
"Tacca",
"M.",
""
],
[
"Taffarello",
"L.",
""
],
[
"Talukder",
"D.",
""
],
[
"Tanner",
"D. B.",
""
],
[
"Tarabrin",
"S. P.",
""
],
[
"Taylor",
"J. R.",
""
],
[
"Taylor",
"R.",
""
],
[
"Thomas",
"P.",
""
],
[
"Thorne",
"K. A.",
""
],
[
"Thorne",
"K. S.",
""
],
[
"Thrane",
"E.",
""
],
[
"Thüring",
"A.",
""
],
[
"Tokmakov",
"K. V.",
""
],
[
"Tomlinson",
"C.",
""
],
[
"Toncelli",
"A.",
""
],
[
"Tonelli",
"M.",
""
],
[
"Torre",
"O.",
""
],
[
"Torres",
"C.",
""
],
[
"Torrie",
"C. I.",
""
],
[
"Tournefier",
"E.",
""
],
[
"Travasso",
"F.",
""
],
[
"Traylor",
"G.",
""
],
[
"Tseng",
"K.",
""
],
[
"Ugolini",
"D.",
""
],
[
"Vahlbruch",
"H.",
""
],
[
"Vajente",
"G.",
""
],
[
"Brand",
"J. F. J. van den",
""
],
[
"Broeck",
"C. Van Den",
""
],
[
"van der Putten",
"S.",
""
],
[
"van Veggel",
"A. A.",
""
],
[
"Vass",
"S.",
""
],
[
"Vasuth",
"M.",
""
],
[
"Vaulin",
"R.",
""
],
[
"Vavoulidis",
"M.",
""
],
[
"Vecchio",
"A.",
""
],
[
"Vedovato",
"G.",
""
],
[
"Veitch",
"J.",
""
],
[
"Veitch",
"P. J.",
""
],
[
"Veltkamp",
"C.",
""
],
[
"Verkindt",
"D.",
""
],
[
"Vetrano",
"F.",
""
],
[
"Viceré",
"A.",
""
],
[
"Villar",
"A. E.",
""
],
[
"Vinet",
"J. -Y.",
""
],
[
"Vitale",
"S.",
""
],
[
"Vitale",
"S.",
""
],
[
"Vocca",
"H.",
""
],
[
"Vorvick",
"C.",
""
],
[
"Vyatchanin",
"S. P.",
""
],
[
"Wade",
"A.",
""
],
[
"Wade",
"L.",
""
],
[
"Wade",
"M.",
""
],
[
"Waldman",
"S. J.",
""
],
[
"Wallace",
"L.",
""
],
[
"Wan",
"Y.",
""
],
[
"Wang",
"M.",
""
],
[
"Wang",
"X.",
""
],
[
"Wang",
"Z.",
""
],
[
"Wanner",
"A.",
""
],
[
"Ward",
"R. L.",
""
],
[
"Was",
"M.",
""
],
[
"Weinert",
"M.",
""
],
[
"Weinstein",
"A. J.",
""
],
[
"Weiss",
"R.",
""
],
[
"Wen",
"L.",
""
],
[
"Wessels",
"P.",
""
],
[
"West",
"M.",
""
],
[
"Westphal",
"T.",
""
],
[
"Wette",
"K.",
""
],
[
"Whelan",
"J. T.",
""
],
[
"Whitcomb",
"S. E.",
""
],
[
"White",
"D. J.",
""
],
[
"Whiting",
"B. F.",
""
],
[
"Wilkinson",
"C.",
""
],
[
"Willems",
"P. A.",
""
],
[
"Williams",
"L.",
""
],
[
"Williams",
"R.",
""
],
[
"Willke",
"B.",
""
],
[
"Winkelmann",
"L.",
""
],
[
"Winkler",
"W.",
""
],
[
"Wipf",
"C. C.",
""
],
[
"Wiseman",
"A. G.",
""
],
[
"Wittel",
"H.",
""
],
[
"Woan",
"G.",
""
],
[
"Wooley",
"R.",
""
],
[
"Worden",
"J.",
""
],
[
"Yakushin",
"I.",
""
],
[
"Yamamoto",
"H.",
""
],
[
"Yamamoto",
"K.",
""
],
[
"Yancey",
"C. C.",
""
],
[
"Yang",
"H.",
""
],
[
"Yeaton-Massey",
"D.",
""
],
[
"Yoshida",
"S.",
""
],
[
"Yu",
"P.",
""
],
[
"Yvert",
"M.",
""
],
[
"Zadroźny",
"A.",
""
],
[
"Zanolin",
"M.",
""
],
[
"Zendri",
"J. -P.",
""
],
[
"Zhang",
"F.",
""
],
[
"Zhang",
"L.",
""
],
[
"Zhang",
"W.",
""
],
[
"Zhao",
"C.",
""
],
[
"Zotov",
"N.",
""
],
[
"Zucker",
"M. E.",
""
],
[
"Zweizig",
"J.",
""
]
] | A stochastic background of gravitational waves is expected to arise from a superposition of many incoherent sources of gravitational waves, of either cosmological or astrophysical origin. This background is a target for the current generation of ground-based detectors. In this article we present the first joint search for a stochastic background using data from the LIGO and Virgo interferometers. In a frequency band of 600-1000 Hz, we obtained a 95% upper limit on the amplitude of $\Omega_{\rm GW}(f) = \Omega_3 (f/900 \mathrm{Hz})^3$, of $\Omega_3 < 0.33$, assuming a value of the Hubble parameter of $h_{100}=0.72$. These new limits are a factor of seven better than the previous best in this frequency band. |
1904.08322 | Rajibul Shaikh | Rajibul Shaikh | Black hole shadow in a general rotating spacetime obtained through
Newman-Janis algorithm | 16 pages, 1 figure, more references added, published in PRD | Phys. Rev. D 100, 024028 (2019) | 10.1103/PhysRevD.100.024028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Newman-Janis (NJ) algorithm has been extensively used in the literature
to generate rotating black hole solutions from nonrotating seed spacetimes. In
this work, we show, using various constants of motion, that the null geodesic
equations in an arbitrary stationary and axially symmetric rotating spacetime
obtained through the NJ algorithm can be separated completely, provided that
the algorithm is applied successfully without any inconsistency. Using the
separated null geodesic equations, we then obtain an analytic general formula
for obtaining the contour of a shadow cast by a compact object whose
gravitational field is given by the arbitrary rotating spacetime under
consideration. As special cases, we apply our general analytic formula to some
known black holes and reproduce the corresponding results for black hole
shadow. Finally, we consider a new example and study shadow using our analytic
general formula.
| [
{
"created": "Wed, 17 Apr 2019 15:39:32 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jul 2019 11:28:40 GMT",
"version": "v2"
}
] | 2019-07-18 | [
[
"Shaikh",
"Rajibul",
""
]
] | The Newman-Janis (NJ) algorithm has been extensively used in the literature to generate rotating black hole solutions from nonrotating seed spacetimes. In this work, we show, using various constants of motion, that the null geodesic equations in an arbitrary stationary and axially symmetric rotating spacetime obtained through the NJ algorithm can be separated completely, provided that the algorithm is applied successfully without any inconsistency. Using the separated null geodesic equations, we then obtain an analytic general formula for obtaining the contour of a shadow cast by a compact object whose gravitational field is given by the arbitrary rotating spacetime under consideration. As special cases, we apply our general analytic formula to some known black holes and reproduce the corresponding results for black hole shadow. Finally, we consider a new example and study shadow using our analytic general formula. |
1006.5027 | Ragab Gad | Ragab M. Gad | On Spherically Symmetric Non-Static Space-Times Admitting Homothetic
Motions | 10 pages, no figures | Nuovo Cim.B124:61-67,2009 | 10.1393/ncb/i2009-10745-3 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Spherically symmetric solutions admitting a homothetic Killing vector field
(HKVF) either orthogonal, $\eta_{\bot}$, or parallel,$\eta_{||}$, to the
4-velocity vector field, $u^a$, are studied. New self-similar solution of
Einstein's field equation is found in the case when HKVF is in a general form.
Some physical properties of the obtained solution are examined.
| [
{
"created": "Wed, 12 May 2010 12:23:06 GMT",
"version": "v1"
}
] | 2015-02-06 | [
[
"Gad",
"Ragab M.",
""
]
] | Spherically symmetric solutions admitting a homothetic Killing vector field (HKVF) either orthogonal, $\eta_{\bot}$, or parallel,$\eta_{||}$, to the 4-velocity vector field, $u^a$, are studied. New self-similar solution of Einstein's field equation is found in the case when HKVF is in a general form. Some physical properties of the obtained solution are examined. |
gr-qc/0208070 | Vladimir Kalashnikov | V. L. Kalashnikov | Quintessential Cosmological Scenarios in the Relativistic Theory of
Gravitation | LaTeX2e, 19 pages, Proc. XXV Int. Workshop on Fundamental Problems of
High Energy Physics and Field Theory (25-28 June 2002, Protvino, Russia) | Geometrical and Topological Ideas in Modern Physics, Petrov V.A.,
Ed. (Protvino, Russia), pp. 250-262 (2003). | null | null | gr-qc | null | It is shown that the accelerated expansion of the universe in the framework
of the relativistic theory of gravitation can be achieved by the introduction
of the quintessential term in the energy-momentum tensor. The value of the
minimum scaling factor and the modern observational data for the density and
state parameters of the matter give the rough estimations for the maximum
graviton mass and the maximum scaling factor. The former can be very low in the
case of the primordial inflation and the latter can be extremely large for the
scalar field model of the quintessence. In any case, the massive graviton stops
the second inflation and provide the closed cosmological scenario in the
agreement with the causality principle inherent to the theory.
| [
{
"created": "Fri, 23 Aug 2002 15:32:52 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Oct 2002 14:45:25 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kalashnikov",
"V. L.",
""
]
] | It is shown that the accelerated expansion of the universe in the framework of the relativistic theory of gravitation can be achieved by the introduction of the quintessential term in the energy-momentum tensor. The value of the minimum scaling factor and the modern observational data for the density and state parameters of the matter give the rough estimations for the maximum graviton mass and the maximum scaling factor. The former can be very low in the case of the primordial inflation and the latter can be extremely large for the scalar field model of the quintessence. In any case, the massive graviton stops the second inflation and provide the closed cosmological scenario in the agreement with the causality principle inherent to the theory. |
1703.06223 | Davide Gerosa | Davide Gerosa, Emanuele Berti | Are merging black holes born from stellar collapse or previous mergers? | 18 pages, 7 figures, 3 tables. Accepted for publication in PRD.
Selected as PRD Editors' Suggestion | Phys. Rev. D 95, 124046 (2017) | 10.1103/PhysRevD.95.124046 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Advanced LIGO detectors at Hanford and Livingston made two confirmed and one
marginal detection of binary black holes during their first observing run. The
first event, GW150914, was from the merger of two black holes much heavier that
those whose masses have been estimated so far, indicating a formation scenario
that might differ from "ordinary" stellar evolution. One possibility is that
these heavy black holes resulted from a previous merger. When the progenitors
of a black hole binary merger result from previous mergers, they should (on
average) merge later, be more massive, and have spin magnitudes clustered
around a dimensionless spin ~0.7. Here we ask the following question: can
gravitational-wave observations determine whether merging black holes were born
from the collapse of massive stars ("first generation"), rather than being the
end product of earlier mergers ("second generation")? We construct simple,
observationally motivated populations of black hole binaries, and we use
Bayesian model selection to show that measurements of the masses, luminosity
distance (or redshift), and "effective spin" of black hole binaries can indeed
distinguish between these different formation scenarios.
| [
{
"created": "Sat, 18 Mar 2017 00:14:29 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Apr 2017 20:10:03 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Jun 2017 20:56:45 GMT",
"version": "v3"
}
] | 2017-06-28 | [
[
"Gerosa",
"Davide",
""
],
[
"Berti",
"Emanuele",
""
]
] | Advanced LIGO detectors at Hanford and Livingston made two confirmed and one marginal detection of binary black holes during their first observing run. The first event, GW150914, was from the merger of two black holes much heavier that those whose masses have been estimated so far, indicating a formation scenario that might differ from "ordinary" stellar evolution. One possibility is that these heavy black holes resulted from a previous merger. When the progenitors of a black hole binary merger result from previous mergers, they should (on average) merge later, be more massive, and have spin magnitudes clustered around a dimensionless spin ~0.7. Here we ask the following question: can gravitational-wave observations determine whether merging black holes were born from the collapse of massive stars ("first generation"), rather than being the end product of earlier mergers ("second generation")? We construct simple, observationally motivated populations of black hole binaries, and we use Bayesian model selection to show that measurements of the masses, luminosity distance (or redshift), and "effective spin" of black hole binaries can indeed distinguish between these different formation scenarios. |
gr-qc/0502074 | Frank Wilczek | Sean P. Robinson and Frank Wilczek | Relationship between Hawking Radiation and Gravitational Anomalies | 5 pages, 1 figure; v2: typo corrected, reference added; v3: comment
added, minor editorial changes to agree with published version | Phys.Rev.Lett.95:011303,2005 | 10.1103/PhysRevLett.95.011303 | MIT-CTP-3561 | gr-qc hep-th | null | We show that in order to avoid a breakdown of general covariance at the
quantum level the total flux in each outgoing partial wave of a quantum field
in a black hole background must be equal to that of a (1+1)-dimensional
blackbody at the Hawking temperature.
| [
{
"created": "Tue, 15 Feb 2005 19:12:16 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Feb 2005 20:30:55 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Aug 2005 21:04:44 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Robinson",
"Sean P.",
""
],
[
"Wilczek",
"Frank",
""
]
] | We show that in order to avoid a breakdown of general covariance at the quantum level the total flux in each outgoing partial wave of a quantum field in a black hole background must be equal to that of a (1+1)-dimensional blackbody at the Hawking temperature. |
gr-qc/0405148 | Gaetano Lambiase | G. Lambiase, G. Papini | Discrete symmetries and the muon's gyro-gravitational ratio in g-2
experiments | 4 pages, no figures | null | null | null | gr-qc | null | We show that recent, persistent discrepancies between theory and experiment
can be interpreted as corrections to the gyro-gravitational ratio of the muon
and lead to improved upper limits on the violation of discrete symmetries in
rotational inertia.
| [
{
"created": "Mon, 31 May 2004 09:53:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lambiase",
"G.",
""
],
[
"Papini",
"G.",
""
]
] | We show that recent, persistent discrepancies between theory and experiment can be interpreted as corrections to the gyro-gravitational ratio of the muon and lead to improved upper limits on the violation of discrete symmetries in rotational inertia. |
1401.2133 | Deniz Olgu Devecioglu | Deniz Olgu Devecioglu | Lifshitz black holes in Einstein-Yang-Mills theory | 23 pages, 8 figures; ver 2: added a new reference | Phys. Rev. D 89, 124020 (2014) | 10.1103/PhysRevD.89.124020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find that the four dimensional cosmological Einstein-Yang-Mills theory
with $SU(2)$ gauge group admits Lifshitz spacetime as a base solution for the
dynamical exponent $z>1$. Motivated by this, we next demonstrate numerically
that the field equations admit black hole solutions which behave regularly on
the horizon and at spatial infinity for different horizon topologies. The
solutions depend on one parameter, the strength of the gauge field at the
horizon, which is fine-tuned to capture the Lifshitz asymptotics at infinity.
We also discuss the behavior of solutions and the change in Hawking temperature
for black holes that are large or small with respect to the length scale $L$,
which is itself fixed by the value of the cosmological constant.
| [
{
"created": "Thu, 9 Jan 2014 19:36:50 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jan 2014 20:50:36 GMT",
"version": "v2"
}
] | 2014-06-25 | [
[
"Devecioglu",
"Deniz Olgu",
""
]
] | We find that the four dimensional cosmological Einstein-Yang-Mills theory with $SU(2)$ gauge group admits Lifshitz spacetime as a base solution for the dynamical exponent $z>1$. Motivated by this, we next demonstrate numerically that the field equations admit black hole solutions which behave regularly on the horizon and at spatial infinity for different horizon topologies. The solutions depend on one parameter, the strength of the gauge field at the horizon, which is fine-tuned to capture the Lifshitz asymptotics at infinity. We also discuss the behavior of solutions and the change in Hawking temperature for black holes that are large or small with respect to the length scale $L$, which is itself fixed by the value of the cosmological constant. |
1202.2836 | Eugeny Babichev | E. Babichev, V. Dokuchaev, Yu. Eroshenko | Backreaction of accreting matter onto a black hole in the
Eddington-Finkelstein coordinates | 12 pages, v.2: references added, typos corrected, matches published
version | Class. Quantum Grav. 29 115002 (2012) | 10.1088/0264-9381/29/11/115002 | LPT-Orsay 12-47 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study backreaction of accreting matter onto a spherically symmetric black
hole in a perturbative way, when accretion is in a quasi-steady state. General
expressions for corrections to the metric coefficients are found in the
Eddington-Finkelstein coordinates. It is shown that near the horizon of a black
hole, independently of the form of the energy-momentum tensor, the leading
corrections to the metric are of the Vaidya form. The relation to other
solutions is discussed and particular examples are presented.
| [
{
"created": "Mon, 13 Feb 2012 20:26:35 GMT",
"version": "v1"
},
{
"created": "Tue, 15 May 2012 10:16:59 GMT",
"version": "v2"
}
] | 2012-05-16 | [
[
"Babichev",
"E.",
""
],
[
"Dokuchaev",
"V.",
""
],
[
"Eroshenko",
"Yu.",
""
]
] | We study backreaction of accreting matter onto a spherically symmetric black hole in a perturbative way, when accretion is in a quasi-steady state. General expressions for corrections to the metric coefficients are found in the Eddington-Finkelstein coordinates. It is shown that near the horizon of a black hole, independently of the form of the energy-momentum tensor, the leading corrections to the metric are of the Vaidya form. The relation to other solutions is discussed and particular examples are presented. |
2110.02278 | Behnoush Afshar | B. Afshar and N. Riazi and H. Moradpour | A note on inflation in dRGT massive gravity | Accepted by The European Physical Jouranal C (2022) | null | 10.1140/epjc/s10052-022-10393-y | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Although the dRGT massive gravity successfully explains the late-time cosmic
acceleration, it cannot justify inflation. On the other hand, and in the
frameworks of General Relativity and modified gravity, the interests and
attempts to describe dark energy and inflation by using Lagranginas, which may
have pole, have recently been enhanced. Subsequently, we are going to show that
this kind of Lagrangian may justify inflation in the framework of dRGT massive
gravity. The study is done focusing on the power and exponential potentials,
and the results show a plausible consistency with the Planck 2018 data and its
combination with BK18 and BAO.
| [
{
"created": "Tue, 5 Oct 2021 18:33:14 GMT",
"version": "v1"
},
{
"created": "Sat, 7 May 2022 07:03:45 GMT",
"version": "v2"
}
] | 2022-05-25 | [
[
"Afshar",
"B.",
""
],
[
"Riazi",
"N.",
""
],
[
"Moradpour",
"H.",
""
]
] | Although the dRGT massive gravity successfully explains the late-time cosmic acceleration, it cannot justify inflation. On the other hand, and in the frameworks of General Relativity and modified gravity, the interests and attempts to describe dark energy and inflation by using Lagranginas, which may have pole, have recently been enhanced. Subsequently, we are going to show that this kind of Lagrangian may justify inflation in the framework of dRGT massive gravity. The study is done focusing on the power and exponential potentials, and the results show a plausible consistency with the Planck 2018 data and its combination with BK18 and BAO. |
2107.12223 | M\`arius Josep Fullana i Alfonso | Neus Puchades Colmenero, Jos\'e Vicente Arnau C\'ordoba and M\`arius
Josep Fullana i Alfonso | Relativistic positioning: including the influence of the gravitational
action of the Sun and the Moon and the Earth's oblateness on Galileo
satellites | 24 pages, 10 figures, original research paper | Astrophysics and Space Science volume 366, Article number: 66
(2021) | 10.1007/s10509-021-03973-z | manuscript number, Manuscrit Number: ASTR-D-21-00090R2 | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Uncertainties in the satellite world lines lead to dominant positioning
errors. In the present work, using the approach presented in \cite{neu14}, a
new analysis of these errors is developed inside a great region surrounding
Earth. This analysis is performed in the framework of the so-called
Relativistic Positioning Systems (RPS). Schwarzschild metric is used to
describe the satellite orbits corresponding to the Galileo Satellites
Constellation. Those orbits are circular with the Earth as their centre. They
are defined as the nominal orbits. The satellite orbits are not circular due to
the perturbations they have and to achieve a more realistic description such
perturbations need to be taken into account. In \cite{neu14} perturbations of
the nominal orbits were statistically simulated. Using the formula from
\cite{col10a} a user location is determined with the four satellites proper
times that the user receives and with the satellite world lines. This formula
can be used with any satellite description, although photons need to travel in
a Minkowskian space-time. For our purposes, the computation of the photon
geodesics in Minkowski space-time is sufficient as demonstrated in
\cite{neu16}. The difference of the user position determined with the nominal
and the perturbed satellite orbits is computed. This difference is defined as
the U-error. Now we compute the perturbed orbits of the satellites considering
a metric that takes into account the gravitational effects of the Earth, the
Moon and the Sun and also the Earth oblateness...
| [
{
"created": "Fri, 23 Jul 2021 17:47:20 GMT",
"version": "v1"
}
] | 2021-07-27 | [
[
"Colmenero",
"Neus Puchades",
""
],
[
"Córdoba",
"José Vicente Arnau",
""
],
[
"Alfonso",
"Màrius Josep Fullana i",
""
]
] | Uncertainties in the satellite world lines lead to dominant positioning errors. In the present work, using the approach presented in \cite{neu14}, a new analysis of these errors is developed inside a great region surrounding Earth. This analysis is performed in the framework of the so-called Relativistic Positioning Systems (RPS). Schwarzschild metric is used to describe the satellite orbits corresponding to the Galileo Satellites Constellation. Those orbits are circular with the Earth as their centre. They are defined as the nominal orbits. The satellite orbits are not circular due to the perturbations they have and to achieve a more realistic description such perturbations need to be taken into account. In \cite{neu14} perturbations of the nominal orbits were statistically simulated. Using the formula from \cite{col10a} a user location is determined with the four satellites proper times that the user receives and with the satellite world lines. This formula can be used with any satellite description, although photons need to travel in a Minkowskian space-time. For our purposes, the computation of the photon geodesics in Minkowski space-time is sufficient as demonstrated in \cite{neu16}. The difference of the user position determined with the nominal and the perturbed satellite orbits is computed. This difference is defined as the U-error. Now we compute the perturbed orbits of the satellites considering a metric that takes into account the gravitational effects of the Earth, the Moon and the Sun and also the Earth oblateness... |
2101.08592 | Jean-Pierre Luminet | Jean-Pierre Luminet (Laboratoire d'Astrophysique de Marseille) | Closed Timelike Curves, Singularities and Causality: A Survey from
G\"odel to Chronological Protection | 11 pages | Universe (2021),7, 12 | 10.3390/universe7010012 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | I give a historical survey of the discussions about the existence of closed
timelike curves in general relativistic models of the universe, opening the
physical possibility of time travel in the past, as first recognized by K.
G\"odel in his rotating universe model of 1949. I emphasize that journeying
into the past is intimately linked to spacetime models devoid of timelike
singularities. Since such singularities arise as an inevitable consequence of
the equations of general relativity given physically reasonable assumptions,
time travel in the past becomes possible only when one or another of these
assumptions is violated. It is the case with wormhole-type solutions. S.
Hawking and other authors have tried to "save" the paradoxical consequences of
time travel in the past by advocating physical mechanisms of chronological
protection; however, such mechanisms remain presently unknown, even when
quantum fluctuations near horizons are taken into account. I close the survey
by a brief and pedestrian discussion of Causal Dynamical Triangulations, an
approach to quantum gravity in which causality plays a seminal role.
| [
{
"created": "Thu, 21 Jan 2021 13:13:01 GMT",
"version": "v1"
}
] | 2021-01-22 | [
[
"Luminet",
"Jean-Pierre",
"",
"Laboratoire d'Astrophysique de Marseille"
]
] | I give a historical survey of the discussions about the existence of closed timelike curves in general relativistic models of the universe, opening the physical possibility of time travel in the past, as first recognized by K. G\"odel in his rotating universe model of 1949. I emphasize that journeying into the past is intimately linked to spacetime models devoid of timelike singularities. Since such singularities arise as an inevitable consequence of the equations of general relativity given physically reasonable assumptions, time travel in the past becomes possible only when one or another of these assumptions is violated. It is the case with wormhole-type solutions. S. Hawking and other authors have tried to "save" the paradoxical consequences of time travel in the past by advocating physical mechanisms of chronological protection; however, such mechanisms remain presently unknown, even when quantum fluctuations near horizons are taken into account. I close the survey by a brief and pedestrian discussion of Causal Dynamical Triangulations, an approach to quantum gravity in which causality plays a seminal role. |
1004.1110 | Antonino Marciano | Antonino Marciano, Giovanni Amelino-Camelia, Nicola Rossano Bruno,
Giulia Gubitosi, Gianluca Mandanici and Alessandro Melchiorri | Interplay between curvature and Planck-scale effects in astrophysics and
cosmology | 26 pages. | JCAP 1006:030,2010 | 10.1088/1475-7516/2010/06/030 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several recent studies have considered the implications for astrophysics and
cosmology of some possible nonclassical properties of spacetime at the Planck
scale. The new effects, such as a Planck-scale-modified energy-momentum
(dispersion) relation, are often inferred from the analysis of some quantum
versions of Minkowski spacetime, and therefore the relevant estimates depend
heavily on the assumption that there could not be significant interplay between
Planck-scale and curvature effects. We here scrutinize this assumption, using
as guidance a quantum version of de Sitter spacetime with known Inonu-Wigner
contraction to a quantum Minkowski spacetime. And we show that, contrary to
common (but unsupported) beliefs, the interplay between Planck-scale and
curvature effects can be significant. Within our illustrative example, in the
Minkowski limit the quantum-geometry deformation parameter is indeed given by
the Planck scale, while in the de Sitter picture the parameter of quantization
of geometry depends both on the Planck scale and the curvature scalar. For the
much-studied case of Planck-scale effects that intervene in the observation of
gamma-ray bursts we can estimate the implications of "quantum spacetime
curvature" within robust simplifying assumptions. For cosmology at the present
stage of the development of the relevant mathematics one cannot go beyond
semiheuristic reasoning, and we here propose a candidate approximate
description of a quantum FRW geometry, obtained by patching together pieces
(with different spacetime curvature) of our quantum de Sitter. This
semiheuristic picture, in spite of its limitations, provides rather robust
evidence that in the early Universe the interplay between Planck-scale and
curvature effects could have been particularly significant.
| [
{
"created": "Wed, 7 Apr 2010 15:16:46 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Marciano",
"Antonino",
""
],
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Bruno",
"Nicola Rossano",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Mandanici",
"Gianluca",
""
],
[
"Melchiorri",
"Alessandro",
""
]
] | Several recent studies have considered the implications for astrophysics and cosmology of some possible nonclassical properties of spacetime at the Planck scale. The new effects, such as a Planck-scale-modified energy-momentum (dispersion) relation, are often inferred from the analysis of some quantum versions of Minkowski spacetime, and therefore the relevant estimates depend heavily on the assumption that there could not be significant interplay between Planck-scale and curvature effects. We here scrutinize this assumption, using as guidance a quantum version of de Sitter spacetime with known Inonu-Wigner contraction to a quantum Minkowski spacetime. And we show that, contrary to common (but unsupported) beliefs, the interplay between Planck-scale and curvature effects can be significant. Within our illustrative example, in the Minkowski limit the quantum-geometry deformation parameter is indeed given by the Planck scale, while in the de Sitter picture the parameter of quantization of geometry depends both on the Planck scale and the curvature scalar. For the much-studied case of Planck-scale effects that intervene in the observation of gamma-ray bursts we can estimate the implications of "quantum spacetime curvature" within robust simplifying assumptions. For cosmology at the present stage of the development of the relevant mathematics one cannot go beyond semiheuristic reasoning, and we here propose a candidate approximate description of a quantum FRW geometry, obtained by patching together pieces (with different spacetime curvature) of our quantum de Sitter. This semiheuristic picture, in spite of its limitations, provides rather robust evidence that in the early Universe the interplay between Planck-scale and curvature effects could have been particularly significant. |
gr-qc/0309129 | Diego Pavon | Narayan Banerjee, Diego Pavon and Somasri Sen | Periodic distribution of galaxies in generalized scalar tensor theory | 8 pages, 4 ps figures, PACS Numbers: 98.65.Dx, 04.50.+h, 95.35.+d,
98.62.Py | Gen.Rel.Grav. 35 (2003) 851-862 | 10.1023/A:1022995104231 | null | gr-qc astro-ph hep-ph | null | With the help of Nordtvedt's scalar tensor theory an exact analytical model
of a non-minimally coupled scalar field cosmology in which the gravitational
coupling $G$ and the Hubble factor $H$ oscillate during the radiation era is
presented. A key feature is that the oscillations are confined to the early
stages of the radiation dominated era with $G$ approaching its present constant
value while $H$ becoming a monotonically decreasing function of time. The Brans
Dicke parameter $\omega$ is chosen to be a function of Brans Dicke scalar field
so that no conflict with observational constraints regarding its present value
arises.
| [
{
"created": "Fri, 26 Sep 2003 15:21:26 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Banerjee",
"Narayan",
""
],
[
"Pavon",
"Diego",
""
],
[
"Sen",
"Somasri",
""
]
] | With the help of Nordtvedt's scalar tensor theory an exact analytical model of a non-minimally coupled scalar field cosmology in which the gravitational coupling $G$ and the Hubble factor $H$ oscillate during the radiation era is presented. A key feature is that the oscillations are confined to the early stages of the radiation dominated era with $G$ approaching its present constant value while $H$ becoming a monotonically decreasing function of time. The Brans Dicke parameter $\omega$ is chosen to be a function of Brans Dicke scalar field so that no conflict with observational constraints regarding its present value arises. |
gr-qc/9507012 | Lior M. Burko | Lior M. Burko | Dipole Perturbations of the Reissner-Nordstrom Solution: The Polar Case | 16 pages, LaTeX, no figures. Submitted for publication in Physical
Review D | Phys.Rev.D52:4518-4526,1995 | 10.1103/PhysRevD.52.4518 | TECHNION-PH-95-5 | gr-qc | null | The formalism developed by Chandrasekhar for the linear polar perturbations
of the Reissner-Nordstrom solution is generalized to include the case of dipole
(l=1) perturbations. Then, the perturbed metric coefficients and components of
the Maxwell tensor are computed.
| [
{
"created": "Thu, 6 Jul 1995 09:45:59 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Burko",
"Lior M.",
""
]
] | The formalism developed by Chandrasekhar for the linear polar perturbations of the Reissner-Nordstrom solution is generalized to include the case of dipole (l=1) perturbations. Then, the perturbed metric coefficients and components of the Maxwell tensor are computed. |
1408.7116 | Zbigniew Haba | Z.Haba | Temperature fluctuations in an inhomogeneous diffusive fluid | 14 pages,minor corrections | Mod.Phys.Lett.A30,1550036(2015) | 10.1142/S0217732315500364 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss metric perturbations of the relativistic diffusion equation around
the homogeneous Juttner equilibrium of massless particles in a homogeneous
expanding universe. The metric perturbation describes matter distribution and
the gravitational wave background in an inhomogeneous universe. We show that
the lowest order perturbation can be treated as a variation of temperature. We
derive a formula expressing temperature fluctuations in terms of the diffusion
and tensor power spectrum. We discuss the multipole expansion of the
fluctuations in the presence of diffusion.
| [
{
"created": "Fri, 29 Aug 2014 19:49:27 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Oct 2014 18:16:55 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Feb 2015 16:49:17 GMT",
"version": "v3"
}
] | 2015-02-27 | [
[
"Haba",
"Z.",
""
]
] | We discuss metric perturbations of the relativistic diffusion equation around the homogeneous Juttner equilibrium of massless particles in a homogeneous expanding universe. The metric perturbation describes matter distribution and the gravitational wave background in an inhomogeneous universe. We show that the lowest order perturbation can be treated as a variation of temperature. We derive a formula expressing temperature fluctuations in terms of the diffusion and tensor power spectrum. We discuss the multipole expansion of the fluctuations in the presence of diffusion. |
1409.4472 | Bahram Mashhoon | B. Mashhoon | Nonlocal Gravity: The General Linear Approximation | 51 pages; v2: Ref. [23] updated | Phys. Rev. D 90, 124031 (2014) | 10.1103/PhysRevD.90.124031 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent classical nonlocal generalization of Einstein's theory of
gravitation is presented within the framework of general relativity via the
introduction of a preferred frame field. The nonlocal generalization of
Einstein's field equations is derived. The linear approximation of nonlocal
gravity (NLG) is thoroughly examined and the solutions of the corresponding
field equations are discussed. It is shown that nonlocality, with a
characteristic length scale of order 1 kpc, simulates dark matter in the linear
regime while preserving causality. Light deflection in linearized nonlocal
gravity is studied in connection with gravitational lensing; in particular, the
propagation of light in the weak gravitational field of a uniformly moving
source is investigated. The astrophysical implications of the results are
briefly mentioned.
| [
{
"created": "Tue, 16 Sep 2014 00:19:20 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Dec 2014 19:41:56 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Mashhoon",
"B.",
""
]
] | The recent classical nonlocal generalization of Einstein's theory of gravitation is presented within the framework of general relativity via the introduction of a preferred frame field. The nonlocal generalization of Einstein's field equations is derived. The linear approximation of nonlocal gravity (NLG) is thoroughly examined and the solutions of the corresponding field equations are discussed. It is shown that nonlocality, with a characteristic length scale of order 1 kpc, simulates dark matter in the linear regime while preserving causality. Light deflection in linearized nonlocal gravity is studied in connection with gravitational lensing; in particular, the propagation of light in the weak gravitational field of a uniformly moving source is investigated. The astrophysical implications of the results are briefly mentioned. |
1006.2230 | Torsten Asselmeyer-Maluga | Torsten Asselmeyer-Maluga and Helge Rose | On the geometrization of matter by exotic smoothness | 30 pages, 3 figures, svjour style, complete reworking now using
Fintushel-Stern knot surgery of elliptic surfaces, discussion of Lorentz
metric and global hyperbolicity for exotic 4-manifolds added, final version
for publication in Gen. Rel. Grav, small typos errors fixed | General Relativity and Gravitation: Volume 44, Issue 11 (2012),
Page 2825-2856 | 10.1007/s10714-012-1419-3 | null | gr-qc hep-th math-ph math.GT math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss the question how matter may emerge from space. For
that purpose we consider the smoothness structure of spacetime as underlying
structure for a geometrical model of matter. For a large class of compact
4-manifolds, the elliptic surfaces, one is able to apply the knot surgery of
Fintushel and Stern to change the smoothness structure. The influence of this
surgery to the Einstein-Hilbert action is discussed. Using the Weierstrass
representation, we are able to show that the knotted torus used in knot surgery
is represented by a spinor fulfilling the Dirac equation and leading to a
mass-less Dirac term in the Einstein-Hilbert action. For sufficient complicated
links and knots, there are "connecting tubes" (graph manifolds, torus bundles)
which introduce an action term of a gauge field. Both terms are genuinely
geometrical and characterized by the mean curvature of the components. We also
discuss the gauge group of the theory to be U(1)xSU(2)xSU(3).
| [
{
"created": "Fri, 11 Jun 2010 08:30:37 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jan 2011 09:51:55 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Jul 2011 20:04:20 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Mar 2012 13:56:58 GMT",
"version": "v4"
},
{
"created": "Wed, 25 Jul 2012 10:28:24 GMT",
"version": "v5"
},
{
"created": "Thu, 26 Jul 2012 09:43:57 GMT",
"version": "v6"
}
] | 2012-10-22 | [
[
"Asselmeyer-Maluga",
"Torsten",
""
],
[
"Rose",
"Helge",
""
]
] | In this paper we discuss the question how matter may emerge from space. For that purpose we consider the smoothness structure of spacetime as underlying structure for a geometrical model of matter. For a large class of compact 4-manifolds, the elliptic surfaces, one is able to apply the knot surgery of Fintushel and Stern to change the smoothness structure. The influence of this surgery to the Einstein-Hilbert action is discussed. Using the Weierstrass representation, we are able to show that the knotted torus used in knot surgery is represented by a spinor fulfilling the Dirac equation and leading to a mass-less Dirac term in the Einstein-Hilbert action. For sufficient complicated links and knots, there are "connecting tubes" (graph manifolds, torus bundles) which introduce an action term of a gauge field. Both terms are genuinely geometrical and characterized by the mean curvature of the components. We also discuss the gauge group of the theory to be U(1)xSU(2)xSU(3). |
2408.06389 | Ion I. Cotaescu | Ion I. Cotaescu | New one-parameter models of dynamical particles in spatially flat FLRW
space-times | 15 pages, 5 figures | null | 10.1140/epjc/s10052-024-13174-x | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | New one-parameter models of non-rotating dynamical particles are derived as
isotropic solutions of Einstein's equations with perfect fluid in space-times
with FLRW asymptotic behaviour generalizing thus the models proposed recently
in [I. I. Cot\u aescu, Eur. Phys. J. C (2022) 82:86]. These particles are
produced by central singularities of the fluid density but without changing the
pressure of the asymptotic FLRW space-times. The principal features of these
models are investigated using a brief graphical analysis for pointing out the
role of the new free parameter. The conclusion is that this gives rise to
families of models which behave as non-rotating black holes in the physical
space domain bordered by the black hole and cosmological horizons.
| [
{
"created": "Sun, 11 Aug 2024 05:27:33 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Cotaescu",
"Ion I.",
""
]
] | New one-parameter models of non-rotating dynamical particles are derived as isotropic solutions of Einstein's equations with perfect fluid in space-times with FLRW asymptotic behaviour generalizing thus the models proposed recently in [I. I. Cot\u aescu, Eur. Phys. J. C (2022) 82:86]. These particles are produced by central singularities of the fluid density but without changing the pressure of the asymptotic FLRW space-times. The principal features of these models are investigated using a brief graphical analysis for pointing out the role of the new free parameter. The conclusion is that this gives rise to families of models which behave as non-rotating black holes in the physical space domain bordered by the black hole and cosmological horizons. |
gr-qc/9503023 | Roland Puntigam | R.A. Puntigam, E. Schr\"ufer, and F.W. Hehl | The Use of Computer Algebra in Maxwell's Theory | 17 pages, LaTeX, uses worldsci.sty, two figures availabel from the
Authors | null | null | Cologne-thp-1995-H5 | gr-qc | null | We present a small computer algebra program for use in Maxwell's theory. The
Maxwell equations and the energy-momentum current of the electromagnetic field
are formulated in the language of exterior differential forms. The
corresponding program can be applied (in the presence of a gravitational field)
in curved Riemannian spacetime as well as in flat Minkowski spacetime in
inertial or {\em non-inertial} frames. Our program is written for the computer
algebra system REDUCE with the help of the EXCALC package for exterior
differential forms.\par The two major advantages of this modern approch to
electrodynamics --- the natural formulation, free of both metric and
coordinates, and the straightforward programming of problems --- are
illustrated by examining a number of examples ranging from the Coulomb field of
a static point charge to the Kerr--Newman solution of the Einstein--Maxwell
equations.
| [
{
"created": "Tue, 14 Mar 1995 18:32:46 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Puntigam",
"R. A.",
""
],
[
"Schrüfer",
"E.",
""
],
[
"Hehl",
"F. W.",
""
]
] | We present a small computer algebra program for use in Maxwell's theory. The Maxwell equations and the energy-momentum current of the electromagnetic field are formulated in the language of exterior differential forms. The corresponding program can be applied (in the presence of a gravitational field) in curved Riemannian spacetime as well as in flat Minkowski spacetime in inertial or {\em non-inertial} frames. Our program is written for the computer algebra system REDUCE with the help of the EXCALC package for exterior differential forms.\par The two major advantages of this modern approch to electrodynamics --- the natural formulation, free of both metric and coordinates, and the straightforward programming of problems --- are illustrated by examining a number of examples ranging from the Coulomb field of a static point charge to the Kerr--Newman solution of the Einstein--Maxwell equations. |
2009.13748 | Hamid Reza Sepangi | Mohaddese Heydari-Fard, Hamid Reza Sepangi | Thin accretion disk signatures of scalarized black holes in
Einstein-scalar-Gauss-Bonnet gravity | 13 pages, 3 figures, to appear in PLB | Phys. Lett. B 816 (2021) 136276 | 10.1016/j.physletb.2021.136276 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein-scalar-Gauss-Bonnet gravity has recently been known to exhibit
spontaneous scalarization. In the presence of the Gauss-Bonnet term the no-hair
theorem can be evaded and novel black hole solutions with non-trivial scalar
fields have been found besides the general relativistic solutions. In this
paper, we aim to investigate the possibility of observationally testing
Einstein-scalar-Gauss-Bonnet gravity using thin accretion disk properties
around such scalarized black holes. Using the Novikov-Thorne model, we
numerically calculate the electromagnetic flux, temperature distribution,
emission spectrum, innermost stable circular orbits and energy conversion
efficiency of accretion disks around such black holes and compare the results
with the standard general relativistic Schwarzschild solution. We find that the
accretion disks around scalarized black holes are hotter and more luminous than
in general relativity.
| [
{
"created": "Tue, 29 Sep 2020 03:29:45 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Apr 2021 08:08:57 GMT",
"version": "v2"
}
] | 2021-04-12 | [
[
"Heydari-Fard",
"Mohaddese",
""
],
[
"Sepangi",
"Hamid Reza",
""
]
] | Einstein-scalar-Gauss-Bonnet gravity has recently been known to exhibit spontaneous scalarization. In the presence of the Gauss-Bonnet term the no-hair theorem can be evaded and novel black hole solutions with non-trivial scalar fields have been found besides the general relativistic solutions. In this paper, we aim to investigate the possibility of observationally testing Einstein-scalar-Gauss-Bonnet gravity using thin accretion disk properties around such scalarized black holes. Using the Novikov-Thorne model, we numerically calculate the electromagnetic flux, temperature distribution, emission spectrum, innermost stable circular orbits and energy conversion efficiency of accretion disks around such black holes and compare the results with the standard general relativistic Schwarzschild solution. We find that the accretion disks around scalarized black holes are hotter and more luminous than in general relativity. |
1902.08207 | Kathryn Zurek | Erik P. Verlinde, Kathryn M. Zurek | Observational Signatures of Quantum Gravity in Interferometers | 6 pages, 1 figure. v2: Updated to reflect published version | null | 10.1016/j.physletb.2021.136663 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the uncertainty in the arm length of an interferometer due to
metric fluctuations from the quantum nature of gravity, proposing a concrete
microscopic model of energy fluctuations in holographic degrees of freedom on
the surface bounding a causally connected region of spacetime. In our model,
fluctuations longitudinal to the beam direction accumulate in the infrared and
feature strong long distance correlation in the transverse direction. This
leads to a signal that could be observed in a gravitational wave
interferometer. We connect the positional uncertainty principle arising from
our calculations to the 't Hooft gravitational S-matrix.
| [
{
"created": "Thu, 21 Feb 2019 19:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 2021 17:45:49 GMT",
"version": "v2"
}
] | 2021-10-22 | [
[
"Verlinde",
"Erik P.",
""
],
[
"Zurek",
"Kathryn M.",
""
]
] | We consider the uncertainty in the arm length of an interferometer due to metric fluctuations from the quantum nature of gravity, proposing a concrete microscopic model of energy fluctuations in holographic degrees of freedom on the surface bounding a causally connected region of spacetime. In our model, fluctuations longitudinal to the beam direction accumulate in the infrared and feature strong long distance correlation in the transverse direction. This leads to a signal that could be observed in a gravitational wave interferometer. We connect the positional uncertainty principle arising from our calculations to the 't Hooft gravitational S-matrix. |
1903.03047 | Sindy Mojica | E. A. Becerra-Vergara, Sindy Mojica, F. D. Lora-Clavijo, and Alejandro
Cruz-Osorio | Anisotropic Quark Stars with an Interacting Quark Equation of State | All comments and suggestions are welcome | Phys. Rev. D 100, 103006 (2019) | 10.1103/PhysRevD.100.103006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A deep exploration of the parameter space that relates the interacting
equation of state with the bag constant B, and the interaction parameter a, is
fundamental for the construction of diverse models of quark stars. In
particular, the anisotropy of quark stars with a well-motivated quantum
chromodynamics (QCD) equation of state is presented here. The contribution of
the fourth order corrections parameter ($\mathrm{a}$) of the QCD perturbation
on the radial and tangential pressure generate significant effects on the
mass-radius relation and the stability of the quark star. An adequate set of
solutions for several values of the bag factor and the interaction parameter
are used in order to calculate the relation between the mass, radius, density,
compactness, and consequently the maximum masses and the stability. Therefore,
while the more interactive quark solution leads to higher masses, the weak
interaction among quarks give solutions similar to the widely known MIT bag
model.
| [
{
"created": "Thu, 7 Mar 2019 17:12:14 GMT",
"version": "v1"
}
] | 2019-11-26 | [
[
"Becerra-Vergara",
"E. A.",
""
],
[
"Mojica",
"Sindy",
""
],
[
"Lora-Clavijo",
"F. D.",
""
],
[
"Cruz-Osorio",
"Alejandro",
""
]
] | A deep exploration of the parameter space that relates the interacting equation of state with the bag constant B, and the interaction parameter a, is fundamental for the construction of diverse models of quark stars. In particular, the anisotropy of quark stars with a well-motivated quantum chromodynamics (QCD) equation of state is presented here. The contribution of the fourth order corrections parameter ($\mathrm{a}$) of the QCD perturbation on the radial and tangential pressure generate significant effects on the mass-radius relation and the stability of the quark star. An adequate set of solutions for several values of the bag factor and the interaction parameter are used in order to calculate the relation between the mass, radius, density, compactness, and consequently the maximum masses and the stability. Therefore, while the more interactive quark solution leads to higher masses, the weak interaction among quarks give solutions similar to the widely known MIT bag model. |
2211.02822 | Tanmoy Paul | Shin'ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul | Modified cosmology from the thermodynamics of apparent horizon | Physics Letters B (PLB) accepted | null | 10.1016/j.physletb.2022.137553 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the realm of the Bekenstein-Hawking entropy, the thermodynamics of
apparent horizon bridges with the usual FLRW
(Friedmann-Lema\^{i}tre-Robertson-Walker) equation only for a special case
where the matter field is given by a perfect fluid having equation of state
(EoS) parameter $= -1$, i.e $p = -\rho$ with $\rho$ and $p$ represent the
energy density and the pressure of the fluid, respectively. To include the case
$p \neq -\rho$, we consider the modification of the Bekenstein-Hawking entropy
in the present work. In particular, we develop an entropy function that leads
to the usual FLRW equations, for a $general$ EoS of the matter fluid given by
$p = w\rho$, directly from the thermodynamics of the apparent horizon. The
newly developed entropy acquires a correction over the Bekenstein-Hawking
entropy and differs from the known entropies like the Tsallis, R\'{e}nyi,
Barrow, Sharma-Mittal, Kaniadakis, and Loop Quantum Gravity entropies proposed
so far. Based on this finding, we examine how the Friedmann equations of the
apparent horizon cosmology are accordingly modified if one starts with a
general entropy depending on the Bekenstein-Hawking entropy. This results in
some interesting cosmological consequences during the early and late stages of
the universe.
| [
{
"created": "Sat, 5 Nov 2022 06:28:44 GMT",
"version": "v1"
}
] | 2022-12-14 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Paul",
"Tanmoy",
""
]
] | In the realm of the Bekenstein-Hawking entropy, the thermodynamics of apparent horizon bridges with the usual FLRW (Friedmann-Lema\^{i}tre-Robertson-Walker) equation only for a special case where the matter field is given by a perfect fluid having equation of state (EoS) parameter $= -1$, i.e $p = -\rho$ with $\rho$ and $p$ represent the energy density and the pressure of the fluid, respectively. To include the case $p \neq -\rho$, we consider the modification of the Bekenstein-Hawking entropy in the present work. In particular, we develop an entropy function that leads to the usual FLRW equations, for a $general$ EoS of the matter fluid given by $p = w\rho$, directly from the thermodynamics of the apparent horizon. The newly developed entropy acquires a correction over the Bekenstein-Hawking entropy and differs from the known entropies like the Tsallis, R\'{e}nyi, Barrow, Sharma-Mittal, Kaniadakis, and Loop Quantum Gravity entropies proposed so far. Based on this finding, we examine how the Friedmann equations of the apparent horizon cosmology are accordingly modified if one starts with a general entropy depending on the Bekenstein-Hawking entropy. This results in some interesting cosmological consequences during the early and late stages of the universe. |
1703.03286 | Paola Dom\'inguez Fern\'andez | Paola Dom\'inguez-Fern\'andez (1), Erik Jim\'enez-V\'azquez (2),
Miguel Alcubierre (2), Edison Montoya (3) and Dar\'io N\'u\~nez (2) ((1)
Argelander Institut f\"ur Astronomie, Universit\"at Bonn, (2) Instituto de
Ciencias Nucleares, Universidad Nacional Aut\'onoma de M\'exico, (3) Escuela
de F\'isica, Universidad Industrial de Santander) | Description of the evolution of inhomogeneities on a Dark Matter halo
with the Vlasov equation | 26 pages, 67 figures, 1 table, submitted to MNRAS | null | 10.1007/s10714-017-2286-8 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a direct numerical integration of the Vlasov equation in spherical
symmetry with a background gravitational potential to determine the evolution
of a collection of particles in different models of a galactic halo. Such a
collection is assumed to represent a dark matter inhomogeneity which reaches a
stationary state determined by the virialization of the system. We describe
some features of the stationary states and, by using several halo models,
obtain distinctive signatures for the evolution of the inhomogeneities in each
of the models.
| [
{
"created": "Tue, 7 Mar 2017 22:03:30 GMT",
"version": "v1"
}
] | 2017-09-06 | [
[
"Domínguez-Fernández",
"Paola",
""
],
[
"Jiménez-Vázquez",
"Erik",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Montoya",
"Edison",
""
],
[
"Núñez",
"Darío",
""
]
] | We use a direct numerical integration of the Vlasov equation in spherical symmetry with a background gravitational potential to determine the evolution of a collection of particles in different models of a galactic halo. Such a collection is assumed to represent a dark matter inhomogeneity which reaches a stationary state determined by the virialization of the system. We describe some features of the stationary states and, by using several halo models, obtain distinctive signatures for the evolution of the inhomogeneities in each of the models. |
2103.09913 | Pratik Wagle | Pratik Wagle, Nicolas Yunes and Hector O. Silva | Quasinormal modes of slowly-rotating black holes in dynamical
Chern-Simons gravity | 28 pages, 6 figures, 15 tables | Phys. Rev. D 105, 124003 (2022) | 10.1103/PhysRevD.105.124003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of gravitational waves from compact binary mergers by the
LIGO/Virgo collaboration has, for the first time, allowed us to test
relativistic gravity in its strong, dynamical and nonlinear regime, thus
opening a new arena to confront general relativity (and modifications thereof)
against observations. We consider a theory which modifies general relativity by
introducing a scalar field coupled to a parity-violating curvature term known
as dynamical Chern-Simons gravity. In this theory, spinning black holes are
different from their general relativistic counterparts and can thus serve as
probes to this theory. We study linear gravito-scalar perturbations of black
holes in dynamical Chern-Simons gravity at leading-order in spin and (i) obtain
the perturbed field equations describing the evolution of the perturbed
gravitational and scalar fields, (ii) numerically solve these equations by
direct integration to calculate the quasinormal mode frequencies for the
dominant and higher multipoles and tabulate them, (iii) find strong evidence
that these rotating black holes are linearly stable, and (iv) present general
fitting functions for different multipoles for gravitational and scalar
quasinormal mode frequencies in terms of spin and Chern-Simons coupling
parameter. Our results can be used to validate the ringdown of small-spin
remnants of numerical relativity simulations of black hole binaries in
dynamical Chern-Simons gravity and pave the way towards future tests of this
theory with gravitational wave ringdown observations.
| [
{
"created": "Wed, 17 Mar 2021 21:17:24 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Aug 2021 16:29:15 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Jun 2022 21:23:57 GMT",
"version": "v3"
}
] | 2022-06-16 | [
[
"Wagle",
"Pratik",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Silva",
"Hector O.",
""
]
] | The detection of gravitational waves from compact binary mergers by the LIGO/Virgo collaboration has, for the first time, allowed us to test relativistic gravity in its strong, dynamical and nonlinear regime, thus opening a new arena to confront general relativity (and modifications thereof) against observations. We consider a theory which modifies general relativity by introducing a scalar field coupled to a parity-violating curvature term known as dynamical Chern-Simons gravity. In this theory, spinning black holes are different from their general relativistic counterparts and can thus serve as probes to this theory. We study linear gravito-scalar perturbations of black holes in dynamical Chern-Simons gravity at leading-order in spin and (i) obtain the perturbed field equations describing the evolution of the perturbed gravitational and scalar fields, (ii) numerically solve these equations by direct integration to calculate the quasinormal mode frequencies for the dominant and higher multipoles and tabulate them, (iii) find strong evidence that these rotating black holes are linearly stable, and (iv) present general fitting functions for different multipoles for gravitational and scalar quasinormal mode frequencies in terms of spin and Chern-Simons coupling parameter. Our results can be used to validate the ringdown of small-spin remnants of numerical relativity simulations of black hole binaries in dynamical Chern-Simons gravity and pave the way towards future tests of this theory with gravitational wave ringdown observations. |
1907.09148 | Hao-Hao Li | Hao-Hao Li and Yun-Song Piao | Time crystals in primordial perturbations | 11 pages, 4 figures, references added, published version | Phys.Lett. B801 (2020) 135156 | 10.1016/j.physletb.2019.135156 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological time crystal (TC) corresponds to a matter state where the
periodic motion of field forms a limit cycle in its phase space. We explore
what would happen if it existed in inflationary phase. It is found that the
limit cycle responsible for TC will inevitably cause the periodic oscillation
of the primordial perturbation spectrum. The oscillatory patterns of the
spectrum depend on the TC parameters, and so encode the crystalline patterns of
TC.
| [
{
"created": "Mon, 22 Jul 2019 06:24:57 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Dec 2019 05:23:33 GMT",
"version": "v2"
}
] | 2019-12-30 | [
[
"Li",
"Hao-Hao",
""
],
[
"Piao",
"Yun-Song",
""
]
] | Cosmological time crystal (TC) corresponds to a matter state where the periodic motion of field forms a limit cycle in its phase space. We explore what would happen if it existed in inflationary phase. It is found that the limit cycle responsible for TC will inevitably cause the periodic oscillation of the primordial perturbation spectrum. The oscillatory patterns of the spectrum depend on the TC parameters, and so encode the crystalline patterns of TC. |
gr-qc/9411019 | Anzhong Wang | Anzhong Wang and Nilton O. Santos | Gravitational and Particle Radiation from Cosmic Strings | 16 pages, Latex, no figures | Class.Quant.Grav.13:715-722,1996 | 10.1088/0264-9381/13/4/011 | null | gr-qc | null | Gravitational and massless particle radiation of straight cosmic strings with
finite thickness is studied analytically. It is found that the non-linear
interaction of the radiation fields emitted by a cosmic string with the ones of
the string always makes the spacetime singular at the symmetry axis. The
singularity is not removable and is a scalar one.
| [
{
"created": "Tue, 8 Nov 1994 12:16:53 GMT",
"version": "v1"
}
] | 2009-07-07 | [
[
"Wang",
"Anzhong",
""
],
[
"Santos",
"Nilton O.",
""
]
] | Gravitational and massless particle radiation of straight cosmic strings with finite thickness is studied analytically. It is found that the non-linear interaction of the radiation fields emitted by a cosmic string with the ones of the string always makes the spacetime singular at the symmetry axis. The singularity is not removable and is a scalar one. |
1309.1990 | Yongsung Yoon | Yongsung Yoon | Conformally Coupled Induced Gravity as an Infrared Fixed Point | 6 pages. arXiv admin note: substantial text overlap with
arXiv:1308.4952, arXiv:0906.4091 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have found that the conformally coupled induced gravity can be an infrared
fixed point of induced gravity with Yukawa couplings with matter. The late time
cosmology with a uniform mean matter distribution can be described by the
conformally coupled induced gravity, which has an emergent global conformal
symmetry in the cosmic scale. Aiming to resolve the puzzles for the dark
energy, we have obtained exact cosmological equations and determined the dark
energy density, the matter density, and the jerk parameter in the present
universe based on the recent observational cosmic expansion data for $a/H^{2}$.
| [
{
"created": "Sun, 8 Sep 2013 18:23:52 GMT",
"version": "v1"
}
] | 2013-09-10 | [
[
"Yoon",
"Yongsung",
""
]
] | We have found that the conformally coupled induced gravity can be an infrared fixed point of induced gravity with Yukawa couplings with matter. The late time cosmology with a uniform mean matter distribution can be described by the conformally coupled induced gravity, which has an emergent global conformal symmetry in the cosmic scale. Aiming to resolve the puzzles for the dark energy, we have obtained exact cosmological equations and determined the dark energy density, the matter density, and the jerk parameter in the present universe based on the recent observational cosmic expansion data for $a/H^{2}$. |
2407.12409 | Nakia Carlevaro | Giovanni Montani, Nakia Carlevaro, Mariaveronica De Angelis | Modified gravity in the presence of matter creation: scenario for the
late Universe | 8 pages, 3 figures | Entropy 26, 662 (2024) | 10.3390/e26080662 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a dynamic scenario for characterizing the late Universe
evolution, aiming to mitigate the Hubble tension. Specifically, we consider a
metric $f(R)$ gravity in the Jordan frame which is implemented to the dynamics
of a flat isotropic Universe. This cosmological model incorporates a matter
creation process, due to the time variation of the cosmological gravitational
field. We model particle creation by representing the isotropic Universe
(specifically, a given fiducial volume) as an open thermodynamic system. The
resulting dynamical model involves four unknowns: the Hubble parameter, the
non-minimally coupled scalar field, its potential, and the energy density of
the matter component. We impose suitable conditions to derive a closed system
for these functions of the redshift. In this model, the vacuum energy density
of the present Universe is determined by the scalar field potential, in line
with the modified gravity scenario. Hence, we construct a viable model,
determining the form of the $f(R)$ theory a posteriori and appropriately
constraining the phenomenological parameters of the matter creation process to
eliminate tachyon modes. Finally, by analyzing the allowed parameter space, we
demonstrate that the Planck evolution of the Hubble parameter can be reconciled
with the late Universe dynamics, thus alleviating the Hubble tension.
| [
{
"created": "Wed, 17 Jul 2024 08:40:05 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Aug 2024 09:17:31 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Montani",
"Giovanni",
""
],
[
"Carlevaro",
"Nakia",
""
],
[
"De Angelis",
"Mariaveronica",
""
]
] | We consider a dynamic scenario for characterizing the late Universe evolution, aiming to mitigate the Hubble tension. Specifically, we consider a metric $f(R)$ gravity in the Jordan frame which is implemented to the dynamics of a flat isotropic Universe. This cosmological model incorporates a matter creation process, due to the time variation of the cosmological gravitational field. We model particle creation by representing the isotropic Universe (specifically, a given fiducial volume) as an open thermodynamic system. The resulting dynamical model involves four unknowns: the Hubble parameter, the non-minimally coupled scalar field, its potential, and the energy density of the matter component. We impose suitable conditions to derive a closed system for these functions of the redshift. In this model, the vacuum energy density of the present Universe is determined by the scalar field potential, in line with the modified gravity scenario. Hence, we construct a viable model, determining the form of the $f(R)$ theory a posteriori and appropriately constraining the phenomenological parameters of the matter creation process to eliminate tachyon modes. Finally, by analyzing the allowed parameter space, we demonstrate that the Planck evolution of the Hubble parameter can be reconciled with the late Universe dynamics, thus alleviating the Hubble tension. |
2304.11092 | Yousef Bisabr | Yousef Bisabr | Attractor Solutions in Interacting Dark Energy Models | 9 pages, 2 figures | Ann. Phys. 458, 169443 (2023) | 10.1016/j.aop.2023.169443 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate a cosmological model in which dark energy, represented by a
quintessential scalar field, is coupled to a dark-matter perfect fluid in the
spatially flat Friedmann-Robertson-Walker Universe. This allows an energy
exchange in the dark sector which could happen both at early times before
recombination era or at late times. We use the coupling function
$Q=\gamma\rho_{dm}\dot{\varphi}$ which is induced by conformal transforming
scalar-tensor and $f(R)$ gravity theories to Einstein frame. It is argued that
there is a connection between this coupling function and $Q\propto \rho_{dm}H$.
A dynamical analysis is used to show that there are early- and late-time
attracting solutions for which the system evolves for a wide range of initial
conditions. These attractors generalize the scaling solutions which have been
already found in the non-interacting case.
| [
{
"created": "Fri, 21 Apr 2023 15:59:41 GMT",
"version": "v1"
}
] | 2023-08-22 | [
[
"Bisabr",
"Yousef",
""
]
] | We investigate a cosmological model in which dark energy, represented by a quintessential scalar field, is coupled to a dark-matter perfect fluid in the spatially flat Friedmann-Robertson-Walker Universe. This allows an energy exchange in the dark sector which could happen both at early times before recombination era or at late times. We use the coupling function $Q=\gamma\rho_{dm}\dot{\varphi}$ which is induced by conformal transforming scalar-tensor and $f(R)$ gravity theories to Einstein frame. It is argued that there is a connection between this coupling function and $Q\propto \rho_{dm}H$. A dynamical analysis is used to show that there are early- and late-time attracting solutions for which the system evolves for a wide range of initial conditions. These attractors generalize the scaling solutions which have been already found in the non-interacting case. |
gr-qc/0303077 | Krsna Dev | Krsna Dev, Marcelo Gleiser | Anisotropic Stars II : Stability | 26 pages 3 figures | Gen.Rel.Grav. 35 (2003) 1435-1457 | 10.1023/A:1024534702166 | null | gr-qc astro-ph | null | We investigate the stability of self-gravitating spherically symmetric
anisotropic spheres under radial perturbations. We consider both the Newtonian
and the full general-relativistic perturbation treatment. In the
general-relativistic case, we extend the variational formalism for spheres with
isotropic pressure developed by Chandrasekhar. We find that, in general, when
the tangential pressure is greater than the radial pressure, the stability of
the anisotropic sphere is enhanced when compared to isotropic configurations.
In particular, anisotropic spheres are found to be stable for smaller values of
the adiabatic index $\gamma$.
| [
{
"created": "Thu, 20 Mar 2003 03:36:41 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Dev",
"Krsna",
""
],
[
"Gleiser",
"Marcelo",
""
]
] | We investigate the stability of self-gravitating spherically symmetric anisotropic spheres under radial perturbations. We consider both the Newtonian and the full general-relativistic perturbation treatment. In the general-relativistic case, we extend the variational formalism for spheres with isotropic pressure developed by Chandrasekhar. We find that, in general, when the tangential pressure is greater than the radial pressure, the stability of the anisotropic sphere is enhanced when compared to isotropic configurations. In particular, anisotropic spheres are found to be stable for smaller values of the adiabatic index $\gamma$. |
0712.0208 | Xin-Zhou Li | Xin-zhou Li, Ping Xi and Xiang-hua Zhai | Global monopole surrounded by quintessence-like matter | 8 pages, 8 figures, added discussion and some references, the form
accepted for publication in Physics Letter B | Phys.Lett.B666:125-130,2008 | 10.1016/j.physletb.2008.06.069 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new static spherically-symmetric solutions of Einstein equations
with the quintessence-like matter surrounding a global monopole. These new
solutions of the coupling scalar-Einstein equations are more complicated, which
depend on the parameter of equation of state $-1 < w_{q} <-{1/3}$. A
gravitating global monopole produces a gravitational field of de Sitter kind
outside the core in addition to a solid angular deficit. In the $w_{q} =
-{1/3}$ case, we have proved that the solution cannot exist since the density
of quintessence-like tends to zero if $w_{q} \to -{1/3}$. As a new feature,
these monopoles have the outer horizon depending on both Goldstone field and
quintessence-like. Since current observations constrain $-1.14 < w_{q} <
-0.93$, new global monopoles have interesting astrophysical applications.
| [
{
"created": "Mon, 3 Dec 2007 03:06:37 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Apr 2008 07:17:19 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Jul 2008 01:57:10 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Li",
"Xin-zhou",
""
],
[
"Xi",
"Ping",
""
],
[
"Zhai",
"Xiang-hua",
""
]
] | We present new static spherically-symmetric solutions of Einstein equations with the quintessence-like matter surrounding a global monopole. These new solutions of the coupling scalar-Einstein equations are more complicated, which depend on the parameter of equation of state $-1 < w_{q} <-{1/3}$. A gravitating global monopole produces a gravitational field of de Sitter kind outside the core in addition to a solid angular deficit. In the $w_{q} = -{1/3}$ case, we have proved that the solution cannot exist since the density of quintessence-like tends to zero if $w_{q} \to -{1/3}$. As a new feature, these monopoles have the outer horizon depending on both Goldstone field and quintessence-like. Since current observations constrain $-1.14 < w_{q} < -0.93$, new global monopoles have interesting astrophysical applications. |
gr-qc/0207067 | Michael Edmund Tobar | Michael Edmund Tobar, John Gideon Hartnett and James David Anstie | Proposal for a New Michelson-Morley Experiment Using a Single Whispering
Spherical Mode Resonator | One pdf. to be published in Phys. Let. A, 2002 | Phys.Lett. A300 (2002) 33-39 | 10.1016/S0375-9601(02)00604-7 | null | gr-qc | null | A new Michelson-Morley experiment is proposed by measuring the beat frequency
of two near degenerate modes with orthogonal propagation in a single spherical
resonator. The unique properties of the experiment allow: 1. Substantial common
mode rejection of some noise sources: 2. Simple calculation of the signal if
Special Relativity is violated. We show that optimum filtering may be used to
increase the signal to noise ratio, and to search for a preferred direction of
the speed of light. Using this technique we show that a sensitivity limit of
order 7.10^-19 is possible by integrating data over one month. We propose
methods to veto systematic effects by correlating the output of more than one
experiment.
| [
{
"created": "Wed, 17 Jul 2002 23:51:25 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Tobar",
"Michael Edmund",
""
],
[
"Hartnett",
"John Gideon",
""
],
[
"Anstie",
"James David",
""
]
] | A new Michelson-Morley experiment is proposed by measuring the beat frequency of two near degenerate modes with orthogonal propagation in a single spherical resonator. The unique properties of the experiment allow: 1. Substantial common mode rejection of some noise sources: 2. Simple calculation of the signal if Special Relativity is violated. We show that optimum filtering may be used to increase the signal to noise ratio, and to search for a preferred direction of the speed of light. Using this technique we show that a sensitivity limit of order 7.10^-19 is possible by integrating data over one month. We propose methods to veto systematic effects by correlating the output of more than one experiment. |
gr-qc/0508016 | Helmut Friedrich | Helmut Friedrich | Is general relativity `essentially understood' ? | Extended version of a talk which was to be delivered at the DPG
Fruehjahrstagung in Berlin, 5 March 2005 | Annalen Phys. 15 (2005) 84-108 | 10.1002/andp.200510173 | null | gr-qc | null | The content of Einstein's theory of gravitation is encoded in the properties
of the solutions to his field equations. There has been obtained a wealth of
information about these solutions in the ninety years the theory has been
around. It led to the prediction and the observation of physical phenomena
which confirm the important role of general relativity in physics. The
understanding of the domain of highly dynamical, strong field configurations
is, however, still quite limited. The gravitational wave experiments are likely
to provide soon observational data on phenomena which are not accessible by
other means. Further theoretical progress will require, however, new methods
for the analysis and the numerical calculation of the solutions to Einstein's
field equations on large scales and under general assumptions. We discuss some
of the problems involved, describe the status of the field and recent results,
and point out some open problems.
| [
{
"created": "Wed, 3 Aug 2005 14:20:09 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Friedrich",
"Helmut",
""
]
] | The content of Einstein's theory of gravitation is encoded in the properties of the solutions to his field equations. There has been obtained a wealth of information about these solutions in the ninety years the theory has been around. It led to the prediction and the observation of physical phenomena which confirm the important role of general relativity in physics. The understanding of the domain of highly dynamical, strong field configurations is, however, still quite limited. The gravitational wave experiments are likely to provide soon observational data on phenomena which are not accessible by other means. Further theoretical progress will require, however, new methods for the analysis and the numerical calculation of the solutions to Einstein's field equations on large scales and under general assumptions. We discuss some of the problems involved, describe the status of the field and recent results, and point out some open problems. |
gr-qc/0412017 | Julio Cesar Fabris | J.C. Fabris | Introduction to cosmology | Latex file, 42 pages. Lectures given at the "Ecole Internationale sur
les structures geometriques et applications", Dakar, Senegal, november 2004.
In French | null | null | null | gr-qc | null | This text consists on a series of introductory lectures on cosmology for
mathematicians and physicists who are not specialized on the subject.
| [
{
"created": "Fri, 3 Dec 2004 17:12:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fabris",
"J. C.",
""
]
] | This text consists on a series of introductory lectures on cosmology for mathematicians and physicists who are not specialized on the subject. |
2303.14136 | Gopi Kant Goswami Dr | Anirudh Pradhan, Gopikant Goswami, Aroonkumar Beesham | The Reconstruction of Constant Jerk Parameter with $f(R,T)$ Gravity | 19 pages 15 figures 1 table | Journal of High Energy Astrophysics 2023 | 10.1016/j.jheap.2023.03.001 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we have developed an FLRW type model of a universe which
displays transition from deceleration in the past to the acceleration at the
present. For this, we have considered field equations of $f(R,T)$ gravity and
have taken $f(R,T) = R + 2 \lambda T$, $\lambda$ being an arbitrary constant.
We have estimated the $\lambda$ parameter in such a way that the transition red
shift is found similar in the deceleration parameter, pressure and the equation
of state parameter $\omega$. The present value of Hubble parameter is estimated
on the basis of the three types of observational data set: latest compilation
of $46$ Hubble data set, SNe Ia $580$ data sets of distance modulus and $66$
Pantheon data set of apparent magnitude which comprised of 40 SN Ia binned and
26 high redshift data's in the range $0.014 \leq z \leq 2.26 $. These data are
compared with theoretical results through the $ \chi^2 $ statistical test.
Interestingly, the model satisfies all the three weak, strong and dominant
energy conditions. The model fits well with observational findings. We have
discussed some of the physical aspects of the model, in particular the age of
the universe.
| [
{
"created": "Thu, 23 Mar 2023 16:53:26 GMT",
"version": "v1"
}
] | 2023-03-27 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Goswami",
"Gopikant",
""
],
[
"Beesham",
"Aroonkumar",
""
]
] | In this work, we have developed an FLRW type model of a universe which displays transition from deceleration in the past to the acceleration at the present. For this, we have considered field equations of $f(R,T)$ gravity and have taken $f(R,T) = R + 2 \lambda T$, $\lambda$ being an arbitrary constant. We have estimated the $\lambda$ parameter in such a way that the transition red shift is found similar in the deceleration parameter, pressure and the equation of state parameter $\omega$. The present value of Hubble parameter is estimated on the basis of the three types of observational data set: latest compilation of $46$ Hubble data set, SNe Ia $580$ data sets of distance modulus and $66$ Pantheon data set of apparent magnitude which comprised of 40 SN Ia binned and 26 high redshift data's in the range $0.014 \leq z \leq 2.26 $. These data are compared with theoretical results through the $ \chi^2 $ statistical test. Interestingly, the model satisfies all the three weak, strong and dominant energy conditions. The model fits well with observational findings. We have discussed some of the physical aspects of the model, in particular the age of the universe. |
1009.2459 | Asrin Abdolmaleki | K. Karami, A. Abdolmaleki | f(T) modified teleparallel gravity models as an alternative for
holographic and new agegraphic dark energy models | 22 pages, 8 figures, the preprint has been improved considerably | Res. Astron. Astrophys. 13 (2013) 757 | 10.1088/1674-4527/13/7/001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we reconstruct different f(T)-gravity models
corresponding to the original and entropy-corrected version of the holographic
and new agegraphic dark energy models. We also obtain the equation of state
parameters of the corresponding f(T)-gravity models. We conclude that the
holographic and new agegraphic f(T)-gravity models behave like phantom or
quintessence model. Whereas in the entropy-corrected models, the equation of
state parameter can justify the transition from the quintessence state to the
phantom regime as indicated by the recent observations.
| [
{
"created": "Mon, 13 Sep 2010 17:44:02 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Aug 2011 04:59:19 GMT",
"version": "v2"
}
] | 2013-07-26 | [
[
"Karami",
"K.",
""
],
[
"Abdolmaleki",
"A.",
""
]
] | In the present work, we reconstruct different f(T)-gravity models corresponding to the original and entropy-corrected version of the holographic and new agegraphic dark energy models. We also obtain the equation of state parameters of the corresponding f(T)-gravity models. We conclude that the holographic and new agegraphic f(T)-gravity models behave like phantom or quintessence model. Whereas in the entropy-corrected models, the equation of state parameter can justify the transition from the quintessence state to the phantom regime as indicated by the recent observations. |
gr-qc/0502069 | Matias Aiello | Matias Aiello, Rafael Ferraro, Gaston Giribet | Hoffmann-Infeld Black Hole Solutions in Lovelock Gravity | 6 pages, 5 figures, Revtex4. References added and comments clarified;
version accepted for publication | Class.Quant.Grav.22:2579-2588,2005 | 10.1088/0264-9381/22/13/004 | null | gr-qc hep-th | null | Five-dimensional black holes are studied in Lovelock gravity coupled to
Hoffmann-Infeld non-linear electrodynamics. It is shown that some of these
solutions present a double peak behavior of the temperature as a function of
the horizon radius. This feature implies that the evaporation process, though
drastic for a period, leads to an eternal black hole remnant. Moreover, the
form of the caloric curve corresponds to the existence of a plateau in the
evaporation rate, which implies that black holes of intermediate scales turn
out to be unstable. The geometrical aspects, such as the absence of conical
singularity, the structure of horizons, etc. are also discussed. In particular,
solutions that are asymptotically AdS arise for special choices of the
parameters, corresponding to charged solutions of five-dimensional Chern-Simons
gravity.
| [
{
"created": "Mon, 14 Feb 2005 20:39:53 GMT",
"version": "v1"
},
{
"created": "Thu, 19 May 2005 17:30:11 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Aiello",
"Matias",
""
],
[
"Ferraro",
"Rafael",
""
],
[
"Giribet",
"Gaston",
""
]
] | Five-dimensional black holes are studied in Lovelock gravity coupled to Hoffmann-Infeld non-linear electrodynamics. It is shown that some of these solutions present a double peak behavior of the temperature as a function of the horizon radius. This feature implies that the evaporation process, though drastic for a period, leads to an eternal black hole remnant. Moreover, the form of the caloric curve corresponds to the existence of a plateau in the evaporation rate, which implies that black holes of intermediate scales turn out to be unstable. The geometrical aspects, such as the absence of conical singularity, the structure of horizons, etc. are also discussed. In particular, solutions that are asymptotically AdS arise for special choices of the parameters, corresponding to charged solutions of five-dimensional Chern-Simons gravity. |
gr-qc/0401085 | Alexander Petrov Nikolaevich | A.N.Petrov | Conserved currents in $D$-dimensional gravity and brane cosmology | LATEX, 6 pages | Vestn.Mosk.Univ.Fiz.Astron. 2 (2004) 10-12; Moscow Univ.Phys.Bull.
59 (2004) 2:11-15 | null | null | gr-qc | null | In $D$-dimentional gravity on arbitrary curved backgrounds using proven
methods conserved currents, divergences of antisymmetrical tensor densities
(superpotentials), are constructed. These superpotentials have two remarkable
properties: they depend in an essential way on second derivatives in the
Lagrangian and are independent on divergences added to it. The conserved
currents are thus particulary well adapted to the case of perturbations in
Gauss-Bonett cosmological brane theories.
| [
{
"created": "Tue, 20 Jan 2004 10:53:22 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Nov 2004 15:59:32 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Petrov",
"A. N.",
""
]
] | In $D$-dimentional gravity on arbitrary curved backgrounds using proven methods conserved currents, divergences of antisymmetrical tensor densities (superpotentials), are constructed. These superpotentials have two remarkable properties: they depend in an essential way on second derivatives in the Lagrangian and are independent on divergences added to it. The conserved currents are thus particulary well adapted to the case of perturbations in Gauss-Bonett cosmological brane theories. |
1401.6974 | Vasilis Oikonomou | V.K. Oikonomou | Fermions in a Reissner-Nordstr\"{o}m-anti-de Sitter Black Hole
Background and $N=4$ Supersymmetry with non-trivial Topological Charges | Substantial changes, presentation changed, reference list updated,
similar to journal version. arXiv admin note: text overlap with
arXiv:1208.0740 | null | 10.1142/S0217732314501314 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that the fermions in Reissner-Nordstr\"{o}m-anti-de Sitter
black hole background in the chiral limit $m=0$, are related to an $N=4$
extended one dimensional supersymmetry with non-trivial topological charges. We
also show that the $N=4$ extended supersymmetry is unbroken and we extend the
two $N=2$ one dimensional supersymmetries that the system also possess, to have
a trivial central charge. The implications of the trivial central charge on the
Witten index are also discussed.
| [
{
"created": "Mon, 27 Jan 2014 19:32:58 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jun 2014 11:18:18 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Oikonomou",
"V. K.",
""
]
] | We demonstrate that the fermions in Reissner-Nordstr\"{o}m-anti-de Sitter black hole background in the chiral limit $m=0$, are related to an $N=4$ extended one dimensional supersymmetry with non-trivial topological charges. We also show that the $N=4$ extended supersymmetry is unbroken and we extend the two $N=2$ one dimensional supersymmetries that the system also possess, to have a trivial central charge. The implications of the trivial central charge on the Witten index are also discussed. |
2104.05566 | Jose Beltran Jimenez | Jose Beltr\'an Jim\'enez and Tomi S. Koivisto | Accidental gauge symmetries of Minkowski spacetime in Teleparallel
theories | 13 pages, no figures. Invited contribution to the Universe Special
Issue "Teleparallel Gravity: Foundations and Observational Constraints". V2:
Extended discussion, added references and typos fixed. Matches published
version | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper, we provide a general framework for the construction of the
Einstein frame within non-linear extensions of the teleparallel equivalents of
General Relativity. These include the metric teleparallel and the symmetric
teleparallel, but also the general teleparallel theories. We write the actions
in a form where we separate the Einstein--Hilbert term, the conformal mode due
to the non-linear nature of the theories (which is analogous to the extra
degree of freedom in $f(R)$ theories), and the sector that manifestly shows the
dynamics arising from the breaking of local symmetries. This frame is then used
to study the theories around the Minkowski background, and we show how all the
non-linear extensions share the same quadratic action around Minkowski. As a
matter of fact, we find that the gauge symmetries that are lost by going to the
non-linear generalisations of the teleparallel General Relativity equivalents
arise as accidental symmetries in the linear theory around Minkowski.
Remarkably, we also find that the conformal mode can be absorbed into a Weyl
rescaling of the metric at this order and, consequently, it disappears from the
linear spectrum so only the usual massless spin 2 perturbation propagates.
These findings unify in a common framework the known fact that no additional
modes propagate on Minkowski backgrounds, and we can trace it back to the
existence of accidental gauge symmetries of such a background.
| [
{
"created": "Mon, 12 Apr 2021 15:33:18 GMT",
"version": "v1"
},
{
"created": "Wed, 12 May 2021 16:26:46 GMT",
"version": "v2"
}
] | 2021-05-13 | [
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Koivisto",
"Tomi S.",
""
]
] | In this paper, we provide a general framework for the construction of the Einstein frame within non-linear extensions of the teleparallel equivalents of General Relativity. These include the metric teleparallel and the symmetric teleparallel, but also the general teleparallel theories. We write the actions in a form where we separate the Einstein--Hilbert term, the conformal mode due to the non-linear nature of the theories (which is analogous to the extra degree of freedom in $f(R)$ theories), and the sector that manifestly shows the dynamics arising from the breaking of local symmetries. This frame is then used to study the theories around the Minkowski background, and we show how all the non-linear extensions share the same quadratic action around Minkowski. As a matter of fact, we find that the gauge symmetries that are lost by going to the non-linear generalisations of the teleparallel General Relativity equivalents arise as accidental symmetries in the linear theory around Minkowski. Remarkably, we also find that the conformal mode can be absorbed into a Weyl rescaling of the metric at this order and, consequently, it disappears from the linear spectrum so only the usual massless spin 2 perturbation propagates. These findings unify in a common framework the known fact that no additional modes propagate on Minkowski backgrounds, and we can trace it back to the existence of accidental gauge symmetries of such a background. |
1708.04971 | Sandipan Sengupta | Sandipan Sengupta | Spacetime-bridge solutions in vacuum gravity | 14 pages, A reference added and a typo corrected | Phys. Rev. D 96, 104031 (2017) | 10.1103/PhysRevD.96.104031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spacetimes, which are representations of a bridge-like geometry in gravity
theory, are constructed as vacuum solutions to the first order equations of
motion. Each such configuration consists of two copies of an asymptotically
flat sheet, connected by a bridge of finite extension where tetrad is
noninvertible. These solutions can be classified into static and non-static
spacetimes. The associated SO(3,1) invariant fields, namely the metric, affine
connection and field-strength tensor, are all continuous across the
hypersurfaces connecting the invertible and noninvertible phases of tetrad and
are finite everywhere. These regular spacetime-bridge solutions do not have any
analogue in Einsteinian gravity in vacuum.
| [
{
"created": "Wed, 16 Aug 2017 16:52:40 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 2017 06:21:31 GMT",
"version": "v2"
}
] | 2017-11-29 | [
[
"Sengupta",
"Sandipan",
""
]
] | Spacetimes, which are representations of a bridge-like geometry in gravity theory, are constructed as vacuum solutions to the first order equations of motion. Each such configuration consists of two copies of an asymptotically flat sheet, connected by a bridge of finite extension where tetrad is noninvertible. These solutions can be classified into static and non-static spacetimes. The associated SO(3,1) invariant fields, namely the metric, affine connection and field-strength tensor, are all continuous across the hypersurfaces connecting the invertible and noninvertible phases of tetrad and are finite everywhere. These regular spacetime-bridge solutions do not have any analogue in Einsteinian gravity in vacuum. |
2102.08438 | Leonardo Giani | Leonardo Giani | Accelerated expansion as manifestation of gravity: when Dark Energy
belongs to the left | PhD thesis, comments are welcome | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In order to explain the Late-times accelerated expansion of the Universe we
must appeal to some form of Dark Energy. In the standard model of cosmology,
the latter is interpreted as a Cosmological Constant $\Lambda$. However, for a
number of reasons, a Cosmological Constant is not completely satisfactory. In
this thesis we study Dark Energy models of geometrical nature, and thus a
manifestation of the underlying gravitational theory. In the first part of the
thesis we will review the $\Lambda$CDM model and give a brief classification of
the landscape of alternative Dark Energy candidates based on the Lovelock
theorem. The second part of the thesis is instead devoted to the presentation
of our main results on the topic of Dark Energy. To begin with, we will report
our studies about nonlocal modifications of gravity involving the differential
operator $\Box^{-1}R$, with emphasis on a specific model and on the common
behavior shared by this and similar theories in the late stages of the
evolution of the Universe. Then we introduce a novel class of modified gravity
theories based on the anticurvature tensor $A^{\mu\nu}$ (the inverse of the
Ricci tensor), and assess their capability as source of Dark Energy. Finally,
we will discuss a type of drift effects which we predicted in the contest of
Strong Gravitational Lensing, which could be employed both to study the
effective equation of state of the Universe and to constrain violations of the
Equivalence Principle.
| [
{
"created": "Tue, 16 Feb 2021 20:25:25 GMT",
"version": "v1"
}
] | 2021-02-18 | [
[
"Giani",
"Leonardo",
""
]
] | In order to explain the Late-times accelerated expansion of the Universe we must appeal to some form of Dark Energy. In the standard model of cosmology, the latter is interpreted as a Cosmological Constant $\Lambda$. However, for a number of reasons, a Cosmological Constant is not completely satisfactory. In this thesis we study Dark Energy models of geometrical nature, and thus a manifestation of the underlying gravitational theory. In the first part of the thesis we will review the $\Lambda$CDM model and give a brief classification of the landscape of alternative Dark Energy candidates based on the Lovelock theorem. The second part of the thesis is instead devoted to the presentation of our main results on the topic of Dark Energy. To begin with, we will report our studies about nonlocal modifications of gravity involving the differential operator $\Box^{-1}R$, with emphasis on a specific model and on the common behavior shared by this and similar theories in the late stages of the evolution of the Universe. Then we introduce a novel class of modified gravity theories based on the anticurvature tensor $A^{\mu\nu}$ (the inverse of the Ricci tensor), and assess their capability as source of Dark Energy. Finally, we will discuss a type of drift effects which we predicted in the contest of Strong Gravitational Lensing, which could be employed both to study the effective equation of state of the Universe and to constrain violations of the Equivalence Principle. |
1604.08140 | Michael Boyle | Michael Boyle | How should spin-weighted spherical functions be defined? | This version corrects a typo in the definition of $K_{\pm}$ above Eq.
(44a). All other equations remain unchanged, including Eqs. (45b) and (46) | J. Math. Phys. 57, 092504 (2016) | 10.1063/1.4962723 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin-weighted spherical functions provide a useful tool for analyzing
tensor-valued functions on the sphere. A tensor field can be decomposed into
complex-valued functions by taking contractions with tangent vectors on the
sphere and the normal to the sphere. These component functions are usually
presented as functions on the sphere itself, but this requires an implicit
choice of distinguished tangent vectors with which to contract. Thus, we may
more accurately say that spin-weighted spherical functions are functions of
both a point on the sphere and a choice of frame in the tangent space at that
point. The distinction becomes extremely important when transforming the
coordinates in which these functions are expressed, because the implicit choice
of frame will also transform. Here, it is proposed that spin-weighted spherical
functions should be treated as functions on the spin group. This approach more
cleanly reflects the geometry involved, and allows for a more elegant
description of the behavior of spin-weighted functions. In this form, the
spin-weighted spherical harmonics have simple expressions as elements of the
Wigner $\mathfrak{D}$ representations, and transformations under rotation are
simple. Two variants of the angular-momentum operator are defined directly in
terms of the spin group; one is the standard angular-momentum operator
$\mathbf{L}$, while the other is shown to be related to the spin-raising
operator $\eth$. Computer code is also included, providing an explicit
implementation of the spin-weighted spherical harmonics in this form.
| [
{
"created": "Wed, 27 Apr 2016 16:54:34 GMT",
"version": "v1"
},
{
"created": "Thu, 26 May 2016 17:56:09 GMT",
"version": "v2"
},
{
"created": "Fri, 23 Sep 2016 13:53:47 GMT",
"version": "v3"
},
{
"created": "Mon, 28 Aug 2023 19:19:24 GMT",
"version": "v4"
}
] | 2023-08-30 | [
[
"Boyle",
"Michael",
""
]
] | Spin-weighted spherical functions provide a useful tool for analyzing tensor-valued functions on the sphere. A tensor field can be decomposed into complex-valued functions by taking contractions with tangent vectors on the sphere and the normal to the sphere. These component functions are usually presented as functions on the sphere itself, but this requires an implicit choice of distinguished tangent vectors with which to contract. Thus, we may more accurately say that spin-weighted spherical functions are functions of both a point on the sphere and a choice of frame in the tangent space at that point. The distinction becomes extremely important when transforming the coordinates in which these functions are expressed, because the implicit choice of frame will also transform. Here, it is proposed that spin-weighted spherical functions should be treated as functions on the spin group. This approach more cleanly reflects the geometry involved, and allows for a more elegant description of the behavior of spin-weighted functions. In this form, the spin-weighted spherical harmonics have simple expressions as elements of the Wigner $\mathfrak{D}$ representations, and transformations under rotation are simple. Two variants of the angular-momentum operator are defined directly in terms of the spin group; one is the standard angular-momentum operator $\mathbf{L}$, while the other is shown to be related to the spin-raising operator $\eth$. Computer code is also included, providing an explicit implementation of the spin-weighted spherical harmonics in this form. |
1011.1843 | Alexander Zhidenko | K. D. Kokkotas, R. A. Konoplya and A. Zhidenko | Quasinormal modes, scattering and Hawking radiation of Kerr-Newman black
holes in a magnetic field | 14 pages, 12 figures | Phys.Rev.D83:024031,2011 | 10.1103/PhysRevD.83.024031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a comprehensive analysis of the spectrum of proper oscillations
(quasinormal modes), transmission/reflection coefficients and Hawking radiation
for a massive charged scalar field in the background of the Kerr-Newman black
hole immersed in an asymptotically homogeneous magnetic field. There are two
main effects: the Zeeman shift of the particle energy in the magnetic field and
the difference of values of an electromagnetic potential between the horizon
and infinity, i.e. the Faraday induction. We have shown that "turning on" the
magnetic field induces a stronger energy-emission rate and leads to
"recharging" of the black hole. Thus, a black hole immersed in a magnetic field
evaporates much quicker, achieving thereby an extremal state in a shorter
period of time. Quasinormal modes are moderately affected by the presence of a
magnetic field which is assumed to be relatively small compared to the
gravitational field of the black hole.
| [
{
"created": "Mon, 8 Nov 2010 16:35:10 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2011 17:55:50 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Kokkotas",
"K. D.",
""
],
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | We perform a comprehensive analysis of the spectrum of proper oscillations (quasinormal modes), transmission/reflection coefficients and Hawking radiation for a massive charged scalar field in the background of the Kerr-Newman black hole immersed in an asymptotically homogeneous magnetic field. There are two main effects: the Zeeman shift of the particle energy in the magnetic field and the difference of values of an electromagnetic potential between the horizon and infinity, i.e. the Faraday induction. We have shown that "turning on" the magnetic field induces a stronger energy-emission rate and leads to "recharging" of the black hole. Thus, a black hole immersed in a magnetic field evaporates much quicker, achieving thereby an extremal state in a shorter period of time. Quasinormal modes are moderately affected by the presence of a magnetic field which is assumed to be relatively small compared to the gravitational field of the black hole. |
2303.16553 | Kei-Ichi Maeda | Kei-ichi Maeda, Priti Gupta, and Hirotada Okawa | Dynamics of Binary System around Supermassive Black Hole | 34 pages,12 figures, 2 tables | null | 10.1103/PhysRevD.107.124039 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We discuss motion of a binary system around a supermassive black hole. Using
Fermi-Walker transport, we construct a local inertial reference frame and set
up a Newtonian binary system. Assuming a circular geodesic observer around a
Schwarzschild black hole, we write down the equations of motion of a binary.
Introducing a small acceleration of the observer, we remove the interaction
terms between the center of mass (CM) of a binary and its relative coordinates.
The CM follows the observer's orbit, but its motion deviates from an exact
circular geodesic. We first solve the relative motion of a binary system, and
then find the motion of the CM by the perturbation equations with the small
acceleration.
We show that there appears the Kozai-Lidov (KL) oscillations when a binary is
compact and the initial inclination is larger than a critical angle. In a hard
binary system, KL oscillations are regular, whereas in a soft binary system,
oscillations are irregular both in period and in amplitude, although stable. We
find an orbital flip when the initial inclination is large. As for the motion
of the CM, the radial deviations from a circular orbit become stable
oscillations with very small amplitude.
| [
{
"created": "Wed, 29 Mar 2023 09:22:07 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Apr 2023 03:04:35 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Apr 2023 07:10:52 GMT",
"version": "v3"
}
] | 2023-06-28 | [
[
"Maeda",
"Kei-ichi",
""
],
[
"Gupta",
"Priti",
""
],
[
"Okawa",
"Hirotada",
""
]
] | We discuss motion of a binary system around a supermassive black hole. Using Fermi-Walker transport, we construct a local inertial reference frame and set up a Newtonian binary system. Assuming a circular geodesic observer around a Schwarzschild black hole, we write down the equations of motion of a binary. Introducing a small acceleration of the observer, we remove the interaction terms between the center of mass (CM) of a binary and its relative coordinates. The CM follows the observer's orbit, but its motion deviates from an exact circular geodesic. We first solve the relative motion of a binary system, and then find the motion of the CM by the perturbation equations with the small acceleration. We show that there appears the Kozai-Lidov (KL) oscillations when a binary is compact and the initial inclination is larger than a critical angle. In a hard binary system, KL oscillations are regular, whereas in a soft binary system, oscillations are irregular both in period and in amplitude, although stable. We find an orbital flip when the initial inclination is large. As for the motion of the CM, the radial deviations from a circular orbit become stable oscillations with very small amplitude. |
1901.05363 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | $f(R)$ Gravity Inflation with String-Corrected Axion Dark Matter | References added, revised version, PRD Accepted | Phys. Rev. D 99, 064049 (2019) | 10.1103/PhysRevD.99.064049 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is quite well known for some time that string inspired axionic terms of
the form $\nu (\phi)\tilde{R}R$, known also as Chern-Simons terms, do not
affect the scalar perturbations and the background evolution for a flat
Friedman-Robertson-Walker Universe. In this paper we study and quantify the
implications of the presence of the above term in the context of vacuum $f(R)$.
Particularly, we assume that axionic dark matter is present during inflation,
and we examine in a quantitative way the effects of axionic Chern-Simons terms
on the tensor perturbations. The axion field is quantified in terms of a
canonical scalar field, with broken Peccei-Quinn symmetry. The model perfectly
describing axions as potential dark matter candidates is based on the so-called
misalignment mechanism, in which case the axion is frozen near its non-zero
vacuum expectation value during early times in which $H\gg m_a$. In effect, the
inflationary era is mainly controlled by the $f(R)$ gravity and the
Chern-Simons term. As we demonstrate, the Chern-Simons term may achieve to make
a non-viable $f(R)$ gravity theory to be phenomenologically viable, due to the
fact that the tensor-to-scalar ratio is significantly reduced, and the same
applies to the spectral index of the tensor perturbations $n_T$. Also by
studying the Starobinsky model in the presence of the Chern-Simons term, we
demonstrate that it is possible to further reduce the amount of primordial
gravitational radiation. The issues of having parity violating gravitational
waves, also the graceful exit from inflation due to axion oscillations and
finally the unification of dark energy-inflation and axion dark matter in the
same $f(R)$ gravity-axion dark matter model, are also briefly discussed.
| [
{
"created": "Wed, 16 Jan 2019 16:11:43 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 2019 16:48:07 GMT",
"version": "v2"
}
] | 2019-04-03 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | It is quite well known for some time that string inspired axionic terms of the form $\nu (\phi)\tilde{R}R$, known also as Chern-Simons terms, do not affect the scalar perturbations and the background evolution for a flat Friedman-Robertson-Walker Universe. In this paper we study and quantify the implications of the presence of the above term in the context of vacuum $f(R)$. Particularly, we assume that axionic dark matter is present during inflation, and we examine in a quantitative way the effects of axionic Chern-Simons terms on the tensor perturbations. The axion field is quantified in terms of a canonical scalar field, with broken Peccei-Quinn symmetry. The model perfectly describing axions as potential dark matter candidates is based on the so-called misalignment mechanism, in which case the axion is frozen near its non-zero vacuum expectation value during early times in which $H\gg m_a$. In effect, the inflationary era is mainly controlled by the $f(R)$ gravity and the Chern-Simons term. As we demonstrate, the Chern-Simons term may achieve to make a non-viable $f(R)$ gravity theory to be phenomenologically viable, due to the fact that the tensor-to-scalar ratio is significantly reduced, and the same applies to the spectral index of the tensor perturbations $n_T$. Also by studying the Starobinsky model in the presence of the Chern-Simons term, we demonstrate that it is possible to further reduce the amount of primordial gravitational radiation. The issues of having parity violating gravitational waves, also the graceful exit from inflation due to axion oscillations and finally the unification of dark energy-inflation and axion dark matter in the same $f(R)$ gravity-axion dark matter model, are also briefly discussed. |
gr-qc/0402102 | D. Petroff | M. Ansorg, T. Fischer, A. Kleinw\"achter, R. Meinel, D. Petroff, K.
Sch\"obel (Theoretisch-Physikalisches Institut, University of Jena) | Equilibrium Configurations of Homogeneous Fluids in General Relativity | 8 pages, colour figures, v3: minor additions including one reference,
accepted by MNRAS | Mon.Not.Roy.Astron.Soc.355:682-688,2004 | 10.1111/j.1365-2966.2004.08371.x | null | gr-qc astro-ph | null | By means of a highly accurate, multi-domain, pseudo-spectral method, we
investigate the solution space of uniformly rotating, homogeneous and
axisymmetric relativistic fluid bodies. It turns out that this space can be
divided up into classes of solutions. In this paper, we present two new classes
including relativistic core-ring and two-ring solutions. Combining our
knowledge of the first four classes with post-Newtonian results and the
Newtonian portion of the first ten classes, we present the qualitative
behaviour of the entire relativistic solution space. The Newtonian disc limit
can only be reached by going through infinitely many of the aforementioned
classes. Only once this limiting process has been consummated, can one proceed
again into the relativistic regime and arrive at the analytically known
relativistic disc of dust.
| [
{
"created": "Tue, 24 Feb 2004 13:42:58 GMT",
"version": "v1"
},
{
"created": "Thu, 13 May 2004 18:27:05 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Aug 2004 10:37:18 GMT",
"version": "v3"
}
] | 2010-12-23 | [
[
"Ansorg",
"M.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
],
[
"Fischer",
"T.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
],
[
"Kleinwächter",
"A.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
],
[
"Meinel",
"R.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
],
[
"Petroff",
"D.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
],
[
"Schöbel",
"K.",
"",
"Theoretisch-Physikalisches Institut, University of Jena"
]
] | By means of a highly accurate, multi-domain, pseudo-spectral method, we investigate the solution space of uniformly rotating, homogeneous and axisymmetric relativistic fluid bodies. It turns out that this space can be divided up into classes of solutions. In this paper, we present two new classes including relativistic core-ring and two-ring solutions. Combining our knowledge of the first four classes with post-Newtonian results and the Newtonian portion of the first ten classes, we present the qualitative behaviour of the entire relativistic solution space. The Newtonian disc limit can only be reached by going through infinitely many of the aforementioned classes. Only once this limiting process has been consummated, can one proceed again into the relativistic regime and arrive at the analytically known relativistic disc of dust. |
2301.00498 | Masato Minamitsuji | Masato Minamitsuji, Antonio De Felice, Shinji Mukohyama, Michele
Oliosi | Gravitational collapse and odd-parity black hole perturbations in
Minimal Theory of Bigravity | 28 pages, published version | Phys. Rev. D 107, 064070 (2023) | 10.1103/PhysRevD.107.064070 | YITP-22-157, IPMU22-0068 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the former part, we study the gravitational collapse of pressureless dust
and find special solutions, where, in both the physical and fiducial sectors,
the exterior and interior spacetime geometries are given by the Schwarzschild
spacetimes and the Friedmann-Lema\^itre-Robertson-Walker universes dominated by
pressureless dust, respectively, with specific time slicings. In the case where
the Lagrange multipliers are trivial and have no jump across the matter
interfaces in both the physical and fiducial sectors, the junction conditions
across them remain the same as those in general relativity (GR). For
simplicity, we foliate the interior geometry by homogeneous and isotropic
spacetimes. For a spatially flat interior universe, we foliate the exterior
geometry by a time-independent flat space, while for a spatiallycurved interior
universe, we foliate the exterior geometry by a time-independent space with
deficit solid angle. Despite the rather restrictive choice of foliations, we
find interesting classes of exact solutions that represent gravitational
collapse in MTBG. In the spatially flat case, under a certain tuning of the
initial condition, we find exact solutions of matter collapse in which the two
sectors evolve independently. In the spatially closed case, once the matter
energy densities and the Schwarzschild radii are tuned between the two sectors,
we find exact solutions that correspond to the Oppenheimer-Snyder model in GR.
In the latter part, we study odd-parity perturbations of the Schwarzschild$-$de
Sitter solutions written in the spatially flat coordinates. For the
higher-multipole modes $\ell\geq2$, we find that, in general, the system
reduces to that of four physical modes, where two of them are dynamical and the
remaining two are shadowy, i.e., satisfying only elliptic equations.
| [
{
"created": "Mon, 2 Jan 2023 01:17:39 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2023 16:07:53 GMT",
"version": "v2"
}
] | 2023-03-31 | [
[
"Minamitsuji",
"Masato",
""
],
[
"De Felice",
"Antonio",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Oliosi",
"Michele",
""
]
] | In the former part, we study the gravitational collapse of pressureless dust and find special solutions, where, in both the physical and fiducial sectors, the exterior and interior spacetime geometries are given by the Schwarzschild spacetimes and the Friedmann-Lema\^itre-Robertson-Walker universes dominated by pressureless dust, respectively, with specific time slicings. In the case where the Lagrange multipliers are trivial and have no jump across the matter interfaces in both the physical and fiducial sectors, the junction conditions across them remain the same as those in general relativity (GR). For simplicity, we foliate the interior geometry by homogeneous and isotropic spacetimes. For a spatially flat interior universe, we foliate the exterior geometry by a time-independent flat space, while for a spatiallycurved interior universe, we foliate the exterior geometry by a time-independent space with deficit solid angle. Despite the rather restrictive choice of foliations, we find interesting classes of exact solutions that represent gravitational collapse in MTBG. In the spatially flat case, under a certain tuning of the initial condition, we find exact solutions of matter collapse in which the two sectors evolve independently. In the spatially closed case, once the matter energy densities and the Schwarzschild radii are tuned between the two sectors, we find exact solutions that correspond to the Oppenheimer-Snyder model in GR. In the latter part, we study odd-parity perturbations of the Schwarzschild$-$de Sitter solutions written in the spatially flat coordinates. For the higher-multipole modes $\ell\geq2$, we find that, in general, the system reduces to that of four physical modes, where two of them are dynamical and the remaining two are shadowy, i.e., satisfying only elliptic equations. |
1410.0199 | Sk Hossein Dr. | Mehedi Kalam, Sk. Monowar Hossein and Sajahan Molla | Isotropic star in low-mass X-ray binaries and X-ray pulsars | 7 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a model for compact stars in the low mass X-ray binaries(LMXBs)
and X-ray pulsars using a metric given by John J. Matese and Patrick G. Whitman
\citep{Matese and Whitman1980}. Here the field equations are reduced to a
system of two algebraic equations considering the isotropic pressure. Compact
star candidates 4U 1820-30(radius=10km) in LMXBs, and Her X-1(radius=7.7km),
SAX J 1808.4-3658(SS1)(radius=7.07km) and SAX J 1808.4-3658(SS2)(radius=6.35km)
in X-ray pulsars satisfy all the energy conditions, TOV-equation and stability
condition. From our model, we have derived mass($M$), central
density($\rho_{0}$), suface density($\rho_{b}$), central pressure($p_{0}$),
surface pressure($p_{b}$) and surface red-shift($Z_{s}$) of the above mentioned
stars, which are very much consistant with the observed/reported datas\citep{N.
K. Glendenning1997,Gondek2000}. We have also observe the adiabatic
index($\gamma$>4/3) of the above steller objects.
| [
{
"created": "Wed, 1 Oct 2014 12:27:38 GMT",
"version": "v1"
}
] | 2014-10-02 | [
[
"Kalam",
"Mehedi",
""
],
[
"Hossein",
"Sk. Monowar",
""
],
[
"Molla",
"Sajahan",
""
]
] | We present a model for compact stars in the low mass X-ray binaries(LMXBs) and X-ray pulsars using a metric given by John J. Matese and Patrick G. Whitman \citep{Matese and Whitman1980}. Here the field equations are reduced to a system of two algebraic equations considering the isotropic pressure. Compact star candidates 4U 1820-30(radius=10km) in LMXBs, and Her X-1(radius=7.7km), SAX J 1808.4-3658(SS1)(radius=7.07km) and SAX J 1808.4-3658(SS2)(radius=6.35km) in X-ray pulsars satisfy all the energy conditions, TOV-equation and stability condition. From our model, we have derived mass($M$), central density($\rho_{0}$), suface density($\rho_{b}$), central pressure($p_{0}$), surface pressure($p_{b}$) and surface red-shift($Z_{s}$) of the above mentioned stars, which are very much consistant with the observed/reported datas\citep{N. K. Glendenning1997,Gondek2000}. We have also observe the adiabatic index($\gamma$>4/3) of the above steller objects. |
gr-qc/0502116 | Makoto Narita | Makoto Narita | On initial conditions and global existence for accelerating cosmologies
from string theory | To appear in Annales Henri Poincare | Annales Henri Poincare 6 (2005) 821-847 | 10.1007/s00023-005-0225-9 | AEI-2005-009 | gr-qc hep-th math-ph math.AP math.MP | null | We construct a solution satisfying initial conditions for accelerating
cosmologies from string/M-theory. Gowdy symmetric spacetimes with a positive
potential are considered. Also, a global existence theorem for the spacetimes
is shown.
| [
{
"created": "Mon, 28 Feb 2005 04:01:19 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Narita",
"Makoto",
""
]
] | We construct a solution satisfying initial conditions for accelerating cosmologies from string/M-theory. Gowdy symmetric spacetimes with a positive potential are considered. Also, a global existence theorem for the spacetimes is shown. |
gr-qc/0001070 | Simon Hern | S. D. Hern (DAMTP, Cambridge) | Coordinate Singularities in Harmonically-sliced Cosmologies | 21 pages, REVTeX, 5 figures | Phys.Rev. D62 (2000) 044003 | 10.1103/PhysRevD.62.044003 | DAMTP-2000-11 | gr-qc | null | Harmonic slicing has in recent years become a standard way of prescribing the
lapse function in numerical simulations of general relativity. However, as was
first noticed by Alcubierre (1997), numerical solutions generated using this
slicing condition can show pathological behaviour. In this paper, analytic and
numerical methods are used to examine harmonic slicings of Kasner and Gowdy
cosmological spacetimes. It is shown that in general the slicings are prevented
from covering the whole of the spacetimes by the appearance of coordinate
singularities. As well as limiting the maximum running times of numerical
simulations, the coordinate singularities can lead to features being produced
in numerically evolved solutions which must be distinguished from genuine
physical effects.
| [
{
"created": "Sun, 23 Jan 2000 15:43:50 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Hern",
"S. D.",
"",
"DAMTP, Cambridge"
]
] | Harmonic slicing has in recent years become a standard way of prescribing the lapse function in numerical simulations of general relativity. However, as was first noticed by Alcubierre (1997), numerical solutions generated using this slicing condition can show pathological behaviour. In this paper, analytic and numerical methods are used to examine harmonic slicings of Kasner and Gowdy cosmological spacetimes. It is shown that in general the slicings are prevented from covering the whole of the spacetimes by the appearance of coordinate singularities. As well as limiting the maximum running times of numerical simulations, the coordinate singularities can lead to features being produced in numerically evolved solutions which must be distinguished from genuine physical effects. |
2210.16383 | Vasilis Oikonomou | S. Nojiri, S.D. Odintsov, V.K. Oikonomou, A. Constantini | Formalizing Anisotropic Inflation in Modified Gravity | NPB Accepted | null | 10.1016/j.nuclphysb.2022.116011 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the fact that the pre-inflationary era may evolve in an exotic
way, in this work we formalize anisotropic evolution in the context of modified
gravity, focusing on pre-inflationary and near the vicinity of the inflationary
epochs. We specialize on specific metrics like Bianchi and Taub and we
formalize the inflationary theory in vacuum $F(R)$ gravity, in $F(R)$ gravity
with an extra scalar field and in Gauss-Bonnet gravity. We discuss the
qualitative effects of the anisotropies on the evolution of the Universe and
also we consider several specific solutions, like the de Sitter solution, in
both the isotropic and anisotropic contexts. Furthermore, several exotic
modified gravity cosmological solutions, like the ones which contain finite
time singularities, are also discussed in brief.
| [
{
"created": "Fri, 28 Oct 2022 19:52:57 GMT",
"version": "v1"
}
] | 2022-11-23 | [
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Constantini",
"A.",
""
]
] | Motivated by the fact that the pre-inflationary era may evolve in an exotic way, in this work we formalize anisotropic evolution in the context of modified gravity, focusing on pre-inflationary and near the vicinity of the inflationary epochs. We specialize on specific metrics like Bianchi and Taub and we formalize the inflationary theory in vacuum $F(R)$ gravity, in $F(R)$ gravity with an extra scalar field and in Gauss-Bonnet gravity. We discuss the qualitative effects of the anisotropies on the evolution of the Universe and also we consider several specific solutions, like the de Sitter solution, in both the isotropic and anisotropic contexts. Furthermore, several exotic modified gravity cosmological solutions, like the ones which contain finite time singularities, are also discussed in brief. |
gr-qc/0208078 | Scott H. Hawley | Scott H. Hawley, Matthew W. Choptuik | Numerical evidence for `multi-scalar stars' | Revtex. 4 pages with 4 figures. Submitted to Phys. Rev. D | Phys.Rev. D67 (2003) 024010 | 10.1103/PhysRevD.67.024010 | AEI-2002-062 | gr-qc astro-ph | null | We present a class of general relativistic soliton-like solutions composed of
multiple minimally coupled, massive, real scalar fields which interact only
through the gravitational field. We describe a two-parameter family of
solutions we call ``phase-shifted boson stars'' (parameterized by central
density rho_0 and phase delta), which are obtained by solving the ordinary
differential equations associated with boson stars and then altering the phase
between the real and imaginary parts of the field. These solutions are similar
to boson stars as well as the oscillating soliton stars found by Seidel and
Suen [E. Seidel and W.M. Suen, Phys. Rev. Lett. 66, 1659 (1991)]; in
particular, long-time numerical evolutions suggest that phase-shifted boson
stars are stable. Our results indicate that scalar soliton-like solutions are
perhaps more generic than has been previously thought.
| [
{
"created": "Mon, 26 Aug 2002 14:18:19 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Nov 2002 00:21:57 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Hawley",
"Scott H.",
""
],
[
"Choptuik",
"Matthew W.",
""
]
] | We present a class of general relativistic soliton-like solutions composed of multiple minimally coupled, massive, real scalar fields which interact only through the gravitational field. We describe a two-parameter family of solutions we call ``phase-shifted boson stars'' (parameterized by central density rho_0 and phase delta), which are obtained by solving the ordinary differential equations associated with boson stars and then altering the phase between the real and imaginary parts of the field. These solutions are similar to boson stars as well as the oscillating soliton stars found by Seidel and Suen [E. Seidel and W.M. Suen, Phys. Rev. Lett. 66, 1659 (1991)]; in particular, long-time numerical evolutions suggest that phase-shifted boson stars are stable. Our results indicate that scalar soliton-like solutions are perhaps more generic than has been previously thought. |
1409.6270 | Jonathan Luk | Xinliang An and Jonathan Luk | Trapped surfaces in vacuum arising dynamically from mild incoming
radiation | null | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the "minimal requirement" on the incoming radiation
that guarantees a trapped surface to form in vacuum. First, we extend the
region of existence in Christodoulou's theorem on the formation of trapped
surfaces and consequently show that the lower bound required to form a trapped
surface can be relaxed. Second, we demonstrate that trapped surfaces form
dynamically from a class of initial data which are large merely in a
scaling-critical norm. This result is motivated in part by the scaling in
Christodoulou's formation of trapped surfaces theorem for the Einstein-scalar
field system in spherical symmetry.
| [
{
"created": "Mon, 22 Sep 2014 18:35:07 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Apr 2017 20:18:44 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"An",
"Xinliang",
""
],
[
"Luk",
"Jonathan",
""
]
] | In this paper, we study the "minimal requirement" on the incoming radiation that guarantees a trapped surface to form in vacuum. First, we extend the region of existence in Christodoulou's theorem on the formation of trapped surfaces and consequently show that the lower bound required to form a trapped surface can be relaxed. Second, we demonstrate that trapped surfaces form dynamically from a class of initial data which are large merely in a scaling-critical norm. This result is motivated in part by the scaling in Christodoulou's formation of trapped surfaces theorem for the Einstein-scalar field system in spherical symmetry. |
2301.04139 | Muhammad Sharif | M. Sharif and Komal Hassan | Electromagnetic Effects on the Complexity of Static Cylindrical Object
in $f(G,T)$ Gravity | 25 pages, 2 figures | Eur. Phys. J. Plus 137(2022)1380 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate complexity of anisotropic cylindrical object
under the influence of electromagnetic field in $f(G,T)$ theory, where $G$ and
$T$ indicate the Gauss-Bonnet term and trace of the stress-energy tensor,
respectively. For this purpose, we calculate the modified field equations,
non-conservation equation and mass distributions that assist in comprehending
the structure of astrophysical objects. The Riemann tensor is divided into
different structure scalars, among which one is called the complexity factor.
This factor is used to measure complexity of the system due to the involvement
of inhomogeneous energy density, anisotropic pressure and charge. The vanishing
of the complexity factor is employed as a constraint to formulate charged
static solutions for the Gokhroo-Mehra model and polytropic equation of state.
We conclude that the presence of charge reduces the complexity of the
anisotropic system.
| [
{
"created": "Tue, 10 Jan 2023 09:03:01 GMT",
"version": "v1"
}
] | 2023-01-12 | [
[
"Sharif",
"M.",
""
],
[
"Hassan",
"Komal",
""
]
] | In this paper, we investigate complexity of anisotropic cylindrical object under the influence of electromagnetic field in $f(G,T)$ theory, where $G$ and $T$ indicate the Gauss-Bonnet term and trace of the stress-energy tensor, respectively. For this purpose, we calculate the modified field equations, non-conservation equation and mass distributions that assist in comprehending the structure of astrophysical objects. The Riemann tensor is divided into different structure scalars, among which one is called the complexity factor. This factor is used to measure complexity of the system due to the involvement of inhomogeneous energy density, anisotropic pressure and charge. The vanishing of the complexity factor is employed as a constraint to formulate charged static solutions for the Gokhroo-Mehra model and polytropic equation of state. We conclude that the presence of charge reduces the complexity of the anisotropic system. |
1111.4921 | Roberto Chan | G. Pinheiro, R. Chan | Radiating Shear-Free Gravitational Collapse with Charge | 22 pages, 9 figures. It has been corrected several typos and included
several references. Accepted for publication in GRG | Gen.Rel.Grav.45:243-261,2013 | 10.1007/s10714-012-1468-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new shear free model for the gravitational collapse of a
spherically symmetric charged body. We propose a dissipative contraction with
radiation emitted outwards. The Einstein field equations, using the junction
conditions and an ansatz, are integrated numerically. A check of the energy
conditions is also performed. We obtain that the charge delays the black hole
formation and it can even halt the collapse.
| [
{
"created": "Mon, 21 Nov 2011 16:37:53 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Jan 2012 13:18:35 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Oct 2012 14:33:48 GMT",
"version": "v3"
}
] | 2013-01-10 | [
[
"Pinheiro",
"G.",
""
],
[
"Chan",
"R.",
""
]
] | We present a new shear free model for the gravitational collapse of a spherically symmetric charged body. We propose a dissipative contraction with radiation emitted outwards. The Einstein field equations, using the junction conditions and an ansatz, are integrated numerically. A check of the energy conditions is also performed. We obtain that the charge delays the black hole formation and it can even halt the collapse. |
1503.08770 | Christian Friedrich Steinwachs | Gianluca Calcagni, Claus Kiefer and Christian F. Steinwachs | What can quantum cosmology say about the inflationary universe? | 13 pages, 2 figures. Contribution to the Proceedings of the DICE14
meeting, Castiglioncello, September 2014 | J. Phys. Conf. Ser. 626 (2015) 1, 012003 | 10.1088/1742-6596/626/1/012003 | FR-PHENO-2015-002 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a method to extract predictions from quantum cosmology for
inflation that can be confronted with observations. Employing the tunneling
boundary condition in quantum geometrodynamics, we derive a probability
distribution for the inflaton field. A sharp peak in this distribution can be
interpreted as setting the initial conditions for the subsequent phase of
inflation. In this way, the peak sets the energy scale at which the
inflationary phase has started. This energy scale must be consistent with the
energy scale found from the inflationary potential and with the scale found
from a potential observation of primordial gravitational waves. Demanding a
consistent history of the universe from its quantum origin to its present
state, which includes decoherence, we derive a condition that allows one to
constrain the parameter space of the underlying model of inflation. We
demonstrate our method by applying it to two models: Higgs inflation and
natural inflation.
| [
{
"created": "Mon, 30 Mar 2015 18:04:36 GMT",
"version": "v1"
}
] | 2015-07-21 | [
[
"Calcagni",
"Gianluca",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Steinwachs",
"Christian F.",
""
]
] | We propose a method to extract predictions from quantum cosmology for inflation that can be confronted with observations. Employing the tunneling boundary condition in quantum geometrodynamics, we derive a probability distribution for the inflaton field. A sharp peak in this distribution can be interpreted as setting the initial conditions for the subsequent phase of inflation. In this way, the peak sets the energy scale at which the inflationary phase has started. This energy scale must be consistent with the energy scale found from the inflationary potential and with the scale found from a potential observation of primordial gravitational waves. Demanding a consistent history of the universe from its quantum origin to its present state, which includes decoherence, we derive a condition that allows one to constrain the parameter space of the underlying model of inflation. We demonstrate our method by applying it to two models: Higgs inflation and natural inflation. |
2401.03667 | Dong-Hoon Kim | Dong-Hoon Kim, Chul Min Kim and Sang Pyo Kim | Quantum refraction effects in pulsar radio emission | 14 pages, 5 figures | Published in Monthly Notices of the Royal Astronomical Society,
531, 2148 on 20 May 2024 | 10.1093/mnras/stae1304 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Highly magnetized neutron stars exhibit the vacuum non-linear electrodynamics
effects, which can be well described using the one-loop effective action for
quantum electrodynamics. In this context, we study the propagation and
polarization of pulsar radio emission, based on the post-Maxwellian Lagrangian
from the Heisenberg-Euler-Schwinger action. Given the refractive index obtained
from this Lagrangian, we determine the leading-order corrections to both the
propagation and polarization vectors due to quantum refraction via perturbation
analysis. In addition, the effects on the orthogonality between the propagation
and polarization vectors and the Faraday rotation angle, all due to quantum
refraction are investigated. Furthermore, from the dual refractive index and
the associated polarization modes, we discuss quantum birefringence, with the
optical phenomenology analogous to its classical counterpart.
| [
{
"created": "Mon, 8 Jan 2024 05:14:25 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2024 03:15:27 GMT",
"version": "v2"
}
] | 2024-06-13 | [
[
"Kim",
"Dong-Hoon",
""
],
[
"Kim",
"Chul Min",
""
],
[
"Kim",
"Sang Pyo",
""
]
] | Highly magnetized neutron stars exhibit the vacuum non-linear electrodynamics effects, which can be well described using the one-loop effective action for quantum electrodynamics. In this context, we study the propagation and polarization of pulsar radio emission, based on the post-Maxwellian Lagrangian from the Heisenberg-Euler-Schwinger action. Given the refractive index obtained from this Lagrangian, we determine the leading-order corrections to both the propagation and polarization vectors due to quantum refraction via perturbation analysis. In addition, the effects on the orthogonality between the propagation and polarization vectors and the Faraday rotation angle, all due to quantum refraction are investigated. Furthermore, from the dual refractive index and the associated polarization modes, we discuss quantum birefringence, with the optical phenomenology analogous to its classical counterpart. |
2004.02636 | Marie-No\"elle C\'el\'erier | Marie-No\"elle C\'el\'erier and Nilton O. Santos | Stationary cylindrical anisotropic fluid and new purely magnetic GR
solutions | 26 pages, 0 figure | Phys. Rev. D 102, 044026 (2020) | 10.1103/PhysRevD.102.044026 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The properties of interior spacetimes sourced by stationary cylindrical
anisotropic fluids are here analytically studied for both nonrigid and rigid
rotation. As regards nonrigid rotation, this is, to our knowledge, the first
work dedicated to such a study. We give here a complete equation set describing
these spacetime properties. In particular, we focus our attention on both
nonrigid and rigid rotation gravito-electromagnetic features and are thus led
to display strong hints in favor of conjecturing purely electric Weyl tensor
existence in this framework. We have also been able to characterize new purely
magnetic physically consistent spacetimes and have found new rigidly rotating
exact solution classes to the five Einstein's field equations pertaining to the
issue and the two purely magnetic constraints we have derived for this purpose.
This should be considered as a prominent result, since extremely few purely
magnetic exact solutions are available in the literature.
| [
{
"created": "Fri, 3 Apr 2020 10:28:56 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Aug 2020 13:55:40 GMT",
"version": "v2"
}
] | 2020-08-19 | [
[
"Célérier",
"Marie-Noëlle",
""
],
[
"Santos",
"Nilton O.",
""
]
] | The properties of interior spacetimes sourced by stationary cylindrical anisotropic fluids are here analytically studied for both nonrigid and rigid rotation. As regards nonrigid rotation, this is, to our knowledge, the first work dedicated to such a study. We give here a complete equation set describing these spacetime properties. In particular, we focus our attention on both nonrigid and rigid rotation gravito-electromagnetic features and are thus led to display strong hints in favor of conjecturing purely electric Weyl tensor existence in this framework. We have also been able to characterize new purely magnetic physically consistent spacetimes and have found new rigidly rotating exact solution classes to the five Einstein's field equations pertaining to the issue and the two purely magnetic constraints we have derived for this purpose. This should be considered as a prominent result, since extremely few purely magnetic exact solutions are available in the literature. |
2401.11591 | Francesco Bajardi | Francesco Bajardi and Daniel Blixt | Primary constraints in general teleparallel quadratic gravity | 24 pages, 1 Figure and 1 Table; Accepted for publication in Physical
Review D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The primary constraints for general teleparallel quadratic gravity are
presented. They provide a basic classification of teleparallel theories from
the perspective of the full nonlinear theory and represent the first step
towards a full-fledged Hamiltonian analysis. The results are consistent with
the limit of metric and symmetric teleparallel quadratic gravity. In the latter
case we also present novel results, since symmetric teleparallel theories have
only been partially studied so far. Apart from the general results, we also
present the special cases of teleparallel theories classically equivalent to
general relativity, which differ by a boundary term from the formulation of
Einstein and Hilbert. This affects the constraint algebra as the primary
constraints involve a mix of torsion and non-metricity, implying that the
symmetries of general relativity are realized in a more intricate way compared
to the teleparallel case. In this context, a more detailed understanding will
provide insights for energy and entropy in gravity, quantum gravity and
numerical relativity of this alternative formulation of general relativity. The
primary constraints are presented both in the standard formulation and in
irreducible parts of torsion and non-metricity. The special role of axial
torsion and its connection to the one-parameter of viable new general
relativity is confirmed. Furthermore, we find that one of the irreducible parts
of non-metricity affects the primary constraint for shift but not lapse.
| [
{
"created": "Sun, 21 Jan 2024 20:43:08 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2024 17:07:07 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Apr 2024 12:39:59 GMT",
"version": "v3"
}
] | 2024-04-29 | [
[
"Bajardi",
"Francesco",
""
],
[
"Blixt",
"Daniel",
""
]
] | The primary constraints for general teleparallel quadratic gravity are presented. They provide a basic classification of teleparallel theories from the perspective of the full nonlinear theory and represent the first step towards a full-fledged Hamiltonian analysis. The results are consistent with the limit of metric and symmetric teleparallel quadratic gravity. In the latter case we also present novel results, since symmetric teleparallel theories have only been partially studied so far. Apart from the general results, we also present the special cases of teleparallel theories classically equivalent to general relativity, which differ by a boundary term from the formulation of Einstein and Hilbert. This affects the constraint algebra as the primary constraints involve a mix of torsion and non-metricity, implying that the symmetries of general relativity are realized in a more intricate way compared to the teleparallel case. In this context, a more detailed understanding will provide insights for energy and entropy in gravity, quantum gravity and numerical relativity of this alternative formulation of general relativity. The primary constraints are presented both in the standard formulation and in irreducible parts of torsion and non-metricity. The special role of axial torsion and its connection to the one-parameter of viable new general relativity is confirmed. Furthermore, we find that one of the irreducible parts of non-metricity affects the primary constraint for shift but not lapse. |
1510.02076 | Mariano Cadoni | Mariano Cadoni and Edgardo Franzin | Black holes sourced by a massless scalar | Talk given at the Karl Schwarzschild Meeting 2015 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct asymptotically flat black hole solutions of Einstein-scalar
gravity sourced by a nontrivial scalar field with 1/r asymptotic behaviour.
Near the singularity the black hole behaves as the Janis-Newmann-Winicour-Wyman
solution. The hairy black hole solutions allow for a consistent thermodynamical
description. At large mass they have the same thermodynamical behaviour of the
Schwarzschild black hole, whereas for small masses they differ substantially
from the latter.
| [
{
"created": "Wed, 7 Oct 2015 19:50:38 GMT",
"version": "v1"
}
] | 2015-10-08 | [
[
"Cadoni",
"Mariano",
""
],
[
"Franzin",
"Edgardo",
""
]
] | We construct asymptotically flat black hole solutions of Einstein-scalar gravity sourced by a nontrivial scalar field with 1/r asymptotic behaviour. Near the singularity the black hole behaves as the Janis-Newmann-Winicour-Wyman solution. The hairy black hole solutions allow for a consistent thermodynamical description. At large mass they have the same thermodynamical behaviour of the Schwarzschild black hole, whereas for small masses they differ substantially from the latter. |
gr-qc/0104056 | null | S. Q. Wu and X. Cai | Asymmetry of Hawking Radiation of Dirac Particles in a Charged Vaidya -
de Sitter Black Hole | 10 pages in 12pt Revtex, no figure, to appear in Int. J. Theor. Phys.
Vol. 40, No.7 (2001) | Int.J.Theor.Phys. 40 (2001) 1349-1357 | null | null | gr-qc | null | The Hawking radiation of Dirac particles in a charged Vaidya - de Sitter
black hole is investigated by using the method of generalized tortoise
coordinate transformation. It is shown that the Hawking radiation of Dirac
particles does not exist for $P_1, Q_2$ components, but for $P_2, Q_1$
components it does. Both the location and the temperature of the event horizon
change with time. The thermal radiation spectrum of Dirac particles is the same
as that of Klein-Gordon particles.
| [
{
"created": "Wed, 18 Apr 2001 02:29:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wu",
"S. Q.",
""
],
[
"Cai",
"X.",
""
]
] | The Hawking radiation of Dirac particles in a charged Vaidya - de Sitter black hole is investigated by using the method of generalized tortoise coordinate transformation. It is shown that the Hawking radiation of Dirac particles does not exist for $P_1, Q_2$ components, but for $P_2, Q_1$ components it does. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein-Gordon particles. |
1509.03135 | Saskia Grunau | Kai Flathmann and Saskia Grunau | Analytic solutions of the geodesic equation for
Einstein-Maxwell-dilaton-axion black holes | title changed due to request of Physical Review D; journal reference
added | Phys. Rev. D 92, 104027 (2015) | 10.1103/PhysRevD.92.104027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study the geodesic motion of test particles and light in
the Einstein-Maxwell-Dilaton-Axion black hole spacetime. We derive the
equations of motion and present their solutions in terms of the Weierstra{\ss}
$\wp$-, $\sigma$- and $\zeta$-functions. With the help of parametric diagrams
and effective potentials we analyze the geodesic motion and give a list of all
possible orbit types.
| [
{
"created": "Thu, 10 Sep 2015 13:07:29 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2015 08:46:10 GMT",
"version": "v2"
}
] | 2015-11-13 | [
[
"Flathmann",
"Kai",
""
],
[
"Grunau",
"Saskia",
""
]
] | In this article we study the geodesic motion of test particles and light in the Einstein-Maxwell-Dilaton-Axion black hole spacetime. We derive the equations of motion and present their solutions in terms of the Weierstra{\ss} $\wp$-, $\sigma$- and $\zeta$-functions. With the help of parametric diagrams and effective potentials we analyze the geodesic motion and give a list of all possible orbit types. |
gr-qc/9808046 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Dimensionful deformations of Poincare' symmetries for a Quantum Gravity
without ideal observers | 7 pages, Latex. (This essay received an ``honorable mention'' from
the Gravity Research Foundation, 1998-Ed.) | Mod.Phys.Lett. A13 (1998) 1319-1325 | 10.1142/S0217732398001376 | NEIP-98-004 | gr-qc | null | Quantum Mechanics is revisited as the appropriate theoretical framework for
the description of the outcome of experiments that rely on the use of classical
devices. In particular, it is emphasized that the limitations on the
measurability of (pairs of conjugate) observables encoded in the formalism of
Quantum Mechanics reproduce faithfully the ``classical-device limit'' of the
corresponding limitations encountered in (real or gedanken) experimental
setups. It is then argued that devices cannot behave classically in Quantum
Gravity, and that this might raise serious problems for the search of a class
of experiments described by theories obtained by ``applying Quantum Mechanics
to Gravity.'' It is also observed that using heuristic/intuitive arguments
based on the absence of classical devices one is led to consider some candidate
Quantum-Gravity phenomena involving dimensionful deformations of the Poincare'
symmetries.
| [
{
"created": "Mon, 17 Aug 1998 14:50:32 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | Quantum Mechanics is revisited as the appropriate theoretical framework for the description of the outcome of experiments that rely on the use of classical devices. In particular, it is emphasized that the limitations on the measurability of (pairs of conjugate) observables encoded in the formalism of Quantum Mechanics reproduce faithfully the ``classical-device limit'' of the corresponding limitations encountered in (real or gedanken) experimental setups. It is then argued that devices cannot behave classically in Quantum Gravity, and that this might raise serious problems for the search of a class of experiments described by theories obtained by ``applying Quantum Mechanics to Gravity.'' It is also observed that using heuristic/intuitive arguments based on the absence of classical devices one is led to consider some candidate Quantum-Gravity phenomena involving dimensionful deformations of the Poincare' symmetries. |
1204.3346 | Stanley P. Gudder | Stan Gudder | A Matter of Matter and Antimatter | 22 pages, including 1 figure | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A discrete quantum gravity model given by a quantum sequential growth process
(QSGP) is considered. The QSGP describes the growth of causal sets (causets)
one element at a time in discrete steps. It is shown that the set $\pscript$ of
causets can be partitioned into three subsets $\pscript = (\rmant)\cup
(\rmmix)\cup (\rmmat)$ where $\rmant$ is the set of pure antimatter causets,
$\rmmat$ the set of pure matter causets and $\rmmix$ the set of mixed
matter-antimatter causets. We observe that there is an asymmetry between
$\rmant$ and $\rmmat$ which may explain the matter-antimatter asymmetry of our
physical universe. This classification of causets extends to the set of paths
$\Omega$ in $\pscript$ to obtain $\Omega =\Omega ^{\rmant}\cup\Omega
^{\rmmix}\cup\Omega ^{\rmmat}$. We introduce a further classification $\Omega
^{\rmmix}=\Omega_{\rmm}^{\rmmix}\cup\Omega_{\rma}^{\rmmix}$ into
matter-antimatter parts. Approximate classical probabilities and quantum
propensities for these various classifications are considered. Some conjectures
and unsolved problems are presented.
| [
{
"created": "Mon, 16 Apr 2012 02:30:52 GMT",
"version": "v1"
}
] | 2012-04-17 | [
[
"Gudder",
"Stan",
""
]
] | A discrete quantum gravity model given by a quantum sequential growth process (QSGP) is considered. The QSGP describes the growth of causal sets (causets) one element at a time in discrete steps. It is shown that the set $\pscript$ of causets can be partitioned into three subsets $\pscript = (\rmant)\cup (\rmmix)\cup (\rmmat)$ where $\rmant$ is the set of pure antimatter causets, $\rmmat$ the set of pure matter causets and $\rmmix$ the set of mixed matter-antimatter causets. We observe that there is an asymmetry between $\rmant$ and $\rmmat$ which may explain the matter-antimatter asymmetry of our physical universe. This classification of causets extends to the set of paths $\Omega$ in $\pscript$ to obtain $\Omega =\Omega ^{\rmant}\cup\Omega ^{\rmmix}\cup\Omega ^{\rmmat}$. We introduce a further classification $\Omega ^{\rmmix}=\Omega_{\rmm}^{\rmmix}\cup\Omega_{\rma}^{\rmmix}$ into matter-antimatter parts. Approximate classical probabilities and quantum propensities for these various classifications are considered. Some conjectures and unsolved problems are presented. |
0904.4295 | Victor M. Villalba | Clara Rojas, Victor M. Villalba | Computation of inflationary cosmological perturbations in chaotic
inflationary scenarios using the phase-integral method | 21 pages, RevTex, to appear in Phys. Rev D | Phys.Rev.D79:103502,2009 | 10.1103/PhysRevD.79.103502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phase-integral approximation devised by Fr\"oman and Fr\"oman, is used
for computing cosmological perturbations in the quadratic chaotic inflationary
model. The phase-integral formulas for the scalar and tensor power spectra are
explicitly obtained up to fifth order of the phase-integral approximation. We
show that, the phase integral gives a very good approximation for the shape of
the power spectra associated with scalar and tensor perturbations as well as
the spectral indices. We find that the accuracy of the phase-integral
approximation compares favorably with the numerical results and those obtained
using the slow-roll and uniform approximation methods.
| [
{
"created": "Tue, 28 Apr 2009 02:33:57 GMT",
"version": "v1"
}
] | 2009-10-29 | [
[
"Rojas",
"Clara",
""
],
[
"Villalba",
"Victor M.",
""
]
] | The phase-integral approximation devised by Fr\"oman and Fr\"oman, is used for computing cosmological perturbations in the quadratic chaotic inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to fifth order of the phase-integral approximation. We show that, the phase integral gives a very good approximation for the shape of the power spectra associated with scalar and tensor perturbations as well as the spectral indices. We find that the accuracy of the phase-integral approximation compares favorably with the numerical results and those obtained using the slow-roll and uniform approximation methods. |
gr-qc/0505052 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Classical and quantum general relativity: a new paradigm | 8 pages, one figure, fifth prize of the Gravity Research Foundation
2005 essay competition | Gen.Rel.Grav.37:1689-1694,2005; Int.J.Mod.Phys.D14:2355-2360,2005 | 10.1142/S0218271805007917 10.1007/s10714-005-0151-7 | LSU-REL-051105 | gr-qc | null | We argue that recent developments in discretizations of classical and quantum
gravity imply a new paradigm for doing research in these areas. The paradigm
consists in discretizing the theory in such a way that the resulting discrete
theory has no constraints. This solves many of the hard conceptual problems of
quantum gravity. It also appears as a useful tool in some numerical simulations
of interest in classical relativity. We outline some of the salient aspects and
results of this new framework.
| [
{
"created": "Wed, 11 May 2005 16:09:31 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We argue that recent developments in discretizations of classical and quantum gravity imply a new paradigm for doing research in these areas. The paradigm consists in discretizing the theory in such a way that the resulting discrete theory has no constraints. This solves many of the hard conceptual problems of quantum gravity. It also appears as a useful tool in some numerical simulations of interest in classical relativity. We outline some of the salient aspects and results of this new framework. |
1201.1640 | Alberto Carrasco Ferreira | Alberto Carrasco Ferreira | Trapped surfaces in spacetimes with symmetries and applications to
uniqueness theorems | 180 pages, 23 figures, Ph.D. Dissertation | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main aim of this thesis is to study the properties of trapped surfaces in
spacetimes with symmetries and their possible relation with the theory of black
holes. We will concetrate specially on one aspect of this possible equivalence,
namely whether the static black hole uniqueness theorems extend to static
spacetimes containing marginally outer trapped surfaces. The principal result
of this thesis states that this question has an affirmative answer, under
suitable not global-in-time conditions on the spacetime. Furthermore, in order
to solve this question, we will obtain several results which generalize known
properties of static spacetimes to the initial data setting and can be of
independent interest. Finally, we will study the Penrose inequality in static
initial data which are not time-symmetric. Our main result in this last part of
the thesis is the discovery of a counter-example of a recent version of the
Penrose inequality proposed by Bray and Khuri in 2009.
| [
{
"created": "Sun, 8 Jan 2012 16:34:20 GMT",
"version": "v1"
}
] | 2015-03-20 | [
[
"Ferreira",
"Alberto Carrasco",
""
]
] | The main aim of this thesis is to study the properties of trapped surfaces in spacetimes with symmetries and their possible relation with the theory of black holes. We will concetrate specially on one aspect of this possible equivalence, namely whether the static black hole uniqueness theorems extend to static spacetimes containing marginally outer trapped surfaces. The principal result of this thesis states that this question has an affirmative answer, under suitable not global-in-time conditions on the spacetime. Furthermore, in order to solve this question, we will obtain several results which generalize known properties of static spacetimes to the initial data setting and can be of independent interest. Finally, we will study the Penrose inequality in static initial data which are not time-symmetric. Our main result in this last part of the thesis is the discovery of a counter-example of a recent version of the Penrose inequality proposed by Bray and Khuri in 2009. |
1611.08106 | Julien Serreau | Maxime Guilleux and Julien Serreau | Nonperturbative renormalization group for scalar fields in de Sitter
space: beyond the local potential approximation | 19 pages, 4 figures ; Published version (PRD) | Phys. Rev. D 95, 045003 (2017) | 10.1103/PhysRevD.95.045003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonperturbative renormalization group techniques have recently proven a
powerful tool to tackle the nontrivial infrared dynamics of light scalar fields
in de Sitter space. In the present article, we develop the formalism beyond the
local potential approximation employed in earlier works. In particular, we
consider the derivative expansion, a systematic expansion in powers of field
derivatives, appropriate for long wavelength modes, that we generalize to the
relevant case of a curved metric with Lorentzian signature. The method is
illustrated with a detailed discussion of the so-called local potential
approximation prime which, on top of the full effective potential, includes a
running (but field-independent) field renormalization. We explicitly compute
the associated anomalous dimension for O(N) theories. We find that it can take
large values along the flow, leading to sizable differences as compared to the
local potential approximation. However, it does not prevent the phenomenon of
gravitationally induced dimensional reduction pointed out in previous studies.
We show that, as a consequence, the effective potential at the end of the flow
is unchanged as compared to the local potential approximation, the main effect
of the running anomalous dimension being merely to slow down the flow.
| [
{
"created": "Thu, 24 Nov 2016 09:07:35 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Feb 2017 10:42:09 GMT",
"version": "v2"
}
] | 2017-02-22 | [
[
"Guilleux",
"Maxime",
""
],
[
"Serreau",
"Julien",
""
]
] | Nonperturbative renormalization group techniques have recently proven a powerful tool to tackle the nontrivial infrared dynamics of light scalar fields in de Sitter space. In the present article, we develop the formalism beyond the local potential approximation employed in earlier works. In particular, we consider the derivative expansion, a systematic expansion in powers of field derivatives, appropriate for long wavelength modes, that we generalize to the relevant case of a curved metric with Lorentzian signature. The method is illustrated with a detailed discussion of the so-called local potential approximation prime which, on top of the full effective potential, includes a running (but field-independent) field renormalization. We explicitly compute the associated anomalous dimension for O(N) theories. We find that it can take large values along the flow, leading to sizable differences as compared to the local potential approximation. However, it does not prevent the phenomenon of gravitationally induced dimensional reduction pointed out in previous studies. We show that, as a consequence, the effective potential at the end of the flow is unchanged as compared to the local potential approximation, the main effect of the running anomalous dimension being merely to slow down the flow. |
1910.00156 | Ulises Nucamendi | Ulises Nucamendi, Ricardo Becerril, Pankaj Sheoran | Bounds on spinning particles in their innermost stable circular orbits
around rotating braneworld black hole | 14 pages, 7 figures | Eur. Phys. J. C (2020) 80:35 | 10.1140/epjc/s10052-019-7584-8 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the innermost stable circular orbit (ISCO) of a spinning test
particle moving in the vicinity of an axially symmetric rotating braneworld
black hole (BH). We start with the description of the event horizon, static
limit surface and ergosphere region of such BH and bring out the effect of
tidal charge parameter on ergosphere. It is found that the ISCO of rotating
braneworld BH is very sensitive to braneworld BH parameter C (also known as
tidal charge parameter) in addition to its rotation parameter. We further
discovered that the orbital radius of the spinning test particles changes non
monotonously with the braneworld BH tidal charge parameter. It is found that
for rotating braneworld BH the allowed range of the particle spin grows as the
tidal charge parameter C decreases, in contrast with the Kerr Newman BH. We
also found the similar behavior of the particles spin for the braneworld
Reissner Nordstrom (C < 0) BH in contrast with its counterpart having (C > 0).
| [
{
"created": "Tue, 1 Oct 2019 00:12:20 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jan 2020 18:22:41 GMT",
"version": "v2"
}
] | 2020-01-24 | [
[
"Nucamendi",
"Ulises",
""
],
[
"Becerril",
"Ricardo",
""
],
[
"Sheoran",
"Pankaj",
""
]
] | We study the innermost stable circular orbit (ISCO) of a spinning test particle moving in the vicinity of an axially symmetric rotating braneworld black hole (BH). We start with the description of the event horizon, static limit surface and ergosphere region of such BH and bring out the effect of tidal charge parameter on ergosphere. It is found that the ISCO of rotating braneworld BH is very sensitive to braneworld BH parameter C (also known as tidal charge parameter) in addition to its rotation parameter. We further discovered that the orbital radius of the spinning test particles changes non monotonously with the braneworld BH tidal charge parameter. It is found that for rotating braneworld BH the allowed range of the particle spin grows as the tidal charge parameter C decreases, in contrast with the Kerr Newman BH. We also found the similar behavior of the particles spin for the braneworld Reissner Nordstrom (C < 0) BH in contrast with its counterpart having (C > 0). |
0901.2437 | Mark Hannam | Mark Hannam, Sascha Husa, John G. Baker, Michael Boyle, Bernd
Bruegmann, Tony Chu, Nils Dorband, Frank Herrmann, Ian Hinder, Bernard J.
Kelly, Lawrence E. Kidder, Pablo Laguna, Keith D. Matthews, James R. van
Meter, Harald P. Pfeiffer, Denis Pollney, Christian Reisswig, Mark A. Scheel,
Deirdre Shoemaker | The Samurai Project: verifying the consistency of black-hole-binary
waveforms for gravitational-wave detection | 17 pages, 9 figures. Version accepted by PRD | Phys.Rev.D79:084025,2009 | 10.1103/PhysRevD.79.084025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We quantify the consistency of numerical-relativity black-hole-binary
waveforms for use in gravitational-wave (GW) searches with current and planned
ground-based detectors. We compare previously published results for the
$(\ell=2,| m | =2)$ mode of the gravitational waves from an equal-mass
nonspinning binary, calculated by five numerical codes. We focus on the 1000M
(about six orbits, or 12 GW cycles) before the peak of the GW amplitude and the
subsequent ringdown. We find that the phase and amplitude agree within each
code's uncertainty estimates. The mismatch between the $(\ell=2,| m| =2)$ modes
is better than $10^{-3}$ for binary masses above $60 M_{\odot}$ with respect to
the Enhanced LIGO detector noise curve, and for masses above $180 M_{\odot}$
with respect to Advanced LIGO, Virgo and Advanced Virgo. Between the waveforms
with the best agreement, the mismatch is below $2 \times 10^{-4}$. We find that
the waveforms would be indistinguishable in all ground-based detectors (and for
the masses we consider) if detected with a signal-to-noise ratio of less than
$\approx14$, or less than $\approx25$ in the best cases.
| [
{
"created": "Fri, 16 Jan 2009 11:32:22 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jan 2009 14:50:59 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Mar 2009 14:56:12 GMT",
"version": "v3"
}
] | 2010-04-14 | [
[
"Hannam",
"Mark",
""
],
[
"Husa",
"Sascha",
""
],
[
"Baker",
"John G.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Chu",
"Tony",
""
],
[
"Dorband",
"Nils",
""
],
[
"Herrmann",
"Frank",
""
],
[
"Hinder",
"Ian",
""
],
[
"Kelly",
"Bernard J.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Matthews",
"Keith D.",
""
],
[
"van Meter",
"James R.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Pollney",
"Denis",
""
],
[
"Reisswig",
"Christian",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | We quantify the consistency of numerical-relativity black-hole-binary waveforms for use in gravitational-wave (GW) searches with current and planned ground-based detectors. We compare previously published results for the $(\ell=2,| m | =2)$ mode of the gravitational waves from an equal-mass nonspinning binary, calculated by five numerical codes. We focus on the 1000M (about six orbits, or 12 GW cycles) before the peak of the GW amplitude and the subsequent ringdown. We find that the phase and amplitude agree within each code's uncertainty estimates. The mismatch between the $(\ell=2,| m| =2)$ modes is better than $10^{-3}$ for binary masses above $60 M_{\odot}$ with respect to the Enhanced LIGO detector noise curve, and for masses above $180 M_{\odot}$ with respect to Advanced LIGO, Virgo and Advanced Virgo. Between the waveforms with the best agreement, the mismatch is below $2 \times 10^{-4}$. We find that the waveforms would be indistinguishable in all ground-based detectors (and for the masses we consider) if detected with a signal-to-noise ratio of less than $\approx14$, or less than $\approx25$ in the best cases. |
gr-qc/0011049 | Ulises Nucamendi | Ulises Nucamendi, Marcelo Salgado and Daniel Sudarsky | An alternative approach to the galactic dark matter problem | 36 pages, 12 figures, Revtex, a brief discussion added, accepted for
publication in PRD | Phys.Rev.D63:125016,2001 | 10.1103/PhysRevD.63.125016 | null | gr-qc astro-ph | null | We discuss scenarios in which the galactic dark matter in spiral galaxies is
described by a long range coherent field which settles in a stationary
configuration that might account for the features of the galactic rotation
curves. The simplest possibility is to consider scalar fields, so we discuss in
particular, two mechanisms that would account for the settlement of the scalar
field in a non-trivial configuration in the absence of a direct coupling of the
field with ordinary matter: topological defects, and spontaneous scalarization.
| [
{
"created": "Tue, 14 Nov 2000 15:57:47 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Feb 2001 11:29:30 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Nucamendi",
"Ulises",
""
],
[
"Salgado",
"Marcelo",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | We discuss scenarios in which the galactic dark matter in spiral galaxies is described by a long range coherent field which settles in a stationary configuration that might account for the features of the galactic rotation curves. The simplest possibility is to consider scalar fields, so we discuss in particular, two mechanisms that would account for the settlement of the scalar field in a non-trivial configuration in the absence of a direct coupling of the field with ordinary matter: topological defects, and spontaneous scalarization. |
2310.08046 | Javlon Rayimbaev Javlon | Sardor Murodov, Javlon Rayimbaev, Bobomurat Ahmedov, Abdullo Hakimov | Dynamics of particles with electric charge and magnetic dipole moment
near Schwarzschild-MOG black hole | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Investigations of electromagnetic interactions between test-charged and
magnetized particles are important in the dynamics of the particles in strong
gravitational fields around black holes. Here, we study the dynamics of a
particle having an electric charge and a magnetic dipole moment in the
spacetime of a Schwarzschild black hole in modified gravity (MOG), called
Schwarzschild-MOG black hole. First, we provide a solution of Maxwell equations
for the angular component of electromagnetic four potentials in the
Schwarzschild-MOG spacetime. Then, we derive equations of motion and effective
potential for circular motion of such particles using a hybrid form of the
Hamilton-Jacobi equation which includes both interactions of electric charge
and magnetic dipole moment with the external magnetic field assumed as
asymptotically uniform, and interaction between the particles and the MOG
field. Also, we investigate the effects of the three types of interactions on
the radius of innermost stable circular orbits (ISCOs) and the energy \&
angular momentum of the particles at their corresponding ISCOs. Finally, we
provide detailed analyses of the effects of the three interactions mentioned
above on the center of mass energy in the collisions between neutral,
electrically charged, and magnetized particles.
| [
{
"created": "Thu, 12 Oct 2023 05:39:28 GMT",
"version": "v1"
}
] | 2023-10-13 | [
[
"Murodov",
"Sardor",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Hakimov",
"Abdullo",
""
]
] | Investigations of electromagnetic interactions between test-charged and magnetized particles are important in the dynamics of the particles in strong gravitational fields around black holes. Here, we study the dynamics of a particle having an electric charge and a magnetic dipole moment in the spacetime of a Schwarzschild black hole in modified gravity (MOG), called Schwarzschild-MOG black hole. First, we provide a solution of Maxwell equations for the angular component of electromagnetic four potentials in the Schwarzschild-MOG spacetime. Then, we derive equations of motion and effective potential for circular motion of such particles using a hybrid form of the Hamilton-Jacobi equation which includes both interactions of electric charge and magnetic dipole moment with the external magnetic field assumed as asymptotically uniform, and interaction between the particles and the MOG field. Also, we investigate the effects of the three types of interactions on the radius of innermost stable circular orbits (ISCOs) and the energy \& angular momentum of the particles at their corresponding ISCOs. Finally, we provide detailed analyses of the effects of the three interactions mentioned above on the center of mass energy in the collisions between neutral, electrically charged, and magnetized particles. |
gr-qc/9911079 | Hiroshi Umetsu | Hisao Suzuki, Eiichi Takasugi and Hiroshi Umetsu | Absorption rate of the Kerr-de Sitter black hole and the Kerr-Newman-de
Sitter black hole | 11 pages, LaTeX. Several typos are corrected | Prog.Theor.Phys. 103 (2000) 723-731 | 10.1143/PTP.103.723 | EPHOU 99-012, OU-HET-333 | gr-qc | null | By using an analytic solution of the Teukolsky equation in the Kerr-de Sitter
and Kerr-Newman-de Sitter geometries, an analytic expression of the absorption
rate formulae for these black holes is calculated.
| [
{
"created": "Mon, 22 Nov 1999 06:48:27 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2000 09:42:42 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Suzuki",
"Hisao",
""
],
[
"Takasugi",
"Eiichi",
""
],
[
"Umetsu",
"Hiroshi",
""
]
] | By using an analytic solution of the Teukolsky equation in the Kerr-de Sitter and Kerr-Newman-de Sitter geometries, an analytic expression of the absorption rate formulae for these black holes is calculated. |
2211.16900 | Elisa Maggio | Elisa Maggio | Probing new physics on the horizon of black holes with gravitational
waves | PhD thesis, 160 pages | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Black holes are the most compact objects in the Universe. According to
general relativity, black holes have a horizon that hides a singularity where
Einstein's theory breaks down. Recently, gravitational waves opened the
possibility to probe the existence of horizons and investigate the nature of
compact objects. This is of particular interest given some quantum-gravity
models which predict the presence of horizonless and singularity-free compact
objects. Such exotic compact objects can emit a different gravitational-wave
signal relative to the black hole case. In this thesis, we analyze the
stability of horizonless compact objects, and derive a generic framework to
compute their characteristic oscillation frequencies. We provide an analytical,
physically-motivated template to search for the gravitational-wave echoes
emitted by these objects in the late-time postmerger signal. Finally, we infer
how extreme mass-ratio inspirals observable by future gravitational-wave
detectors will allow for model-independent tests of the black hole paradigm.
| [
{
"created": "Wed, 30 Nov 2022 10:58:31 GMT",
"version": "v1"
}
] | 2022-12-01 | [
[
"Maggio",
"Elisa",
""
]
] | Black holes are the most compact objects in the Universe. According to general relativity, black holes have a horizon that hides a singularity where Einstein's theory breaks down. Recently, gravitational waves opened the possibility to probe the existence of horizons and investigate the nature of compact objects. This is of particular interest given some quantum-gravity models which predict the presence of horizonless and singularity-free compact objects. Such exotic compact objects can emit a different gravitational-wave signal relative to the black hole case. In this thesis, we analyze the stability of horizonless compact objects, and derive a generic framework to compute their characteristic oscillation frequencies. We provide an analytical, physically-motivated template to search for the gravitational-wave echoes emitted by these objects in the late-time postmerger signal. Finally, we infer how extreme mass-ratio inspirals observable by future gravitational-wave detectors will allow for model-independent tests of the black hole paradigm. |
1605.03942 | Matti Raasakka | Matti Raasakka | Spacetime-Free Approach to Quantum Theory and Effective Spacetime
Structure | null | SIGMA 13 (2017), 006, 33 pages | 10.3842/SIGMA.2017.006 | null | gr-qc hep-th math-ph math.MP quant-ph | http://creativecommons.org/licenses/by-sa/4.0/ | Motivated by hints of the effective emergent nature of spacetime structure,
we formulate a spacetime-free algebraic framework for quantum theory, in which
no a priori background geometric structure is required. Such a framework is
necessary in order to study the emergence of effective spacetime structure in a
consistent manner, without assuming a background geometry from the outset.
Instead, the background geometry is conjectured to arise as an effective
structure of the algebraic and dynamical relations between observables that are
imposed by the background statistics of the system. Namely, we suggest that
quantum reference states on an extended observable algebra, the free algebra
generated by the observables, may give rise to effective spacetime structures.
Accordingly, perturbations of the reference state lead to perturbations of the
induced effective spacetime geometry. We initiate the study of these
perturbations, and their relation to gravitational phenomena.
| [
{
"created": "Thu, 12 May 2016 19:25:58 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2017 05:05:45 GMT",
"version": "v2"
}
] | 2017-01-25 | [
[
"Raasakka",
"Matti",
""
]
] | Motivated by hints of the effective emergent nature of spacetime structure, we formulate a spacetime-free algebraic framework for quantum theory, in which no a priori background geometric structure is required. Such a framework is necessary in order to study the emergence of effective spacetime structure in a consistent manner, without assuming a background geometry from the outset. Instead, the background geometry is conjectured to arise as an effective structure of the algebraic and dynamical relations between observables that are imposed by the background statistics of the system. Namely, we suggest that quantum reference states on an extended observable algebra, the free algebra generated by the observables, may give rise to effective spacetime structures. Accordingly, perturbations of the reference state lead to perturbations of the induced effective spacetime geometry. We initiate the study of these perturbations, and their relation to gravitational phenomena. |
1008.2805 | Muhammad Sharif | M. Sharif and G. Abbas | Gravitational Collapse: Expanding and Collapsing Regions | 12 pages, 4 figures, accepted for publication in Gen. Relativ. Grav | Gen.Rel.Grav.43:1179-1188,2011 | 10.1007/s10714-010-0952-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the expanding and collapsing regions by taking two well-known
spherically symmetric spacetimes. For this purpose, the general formalism is
developed by using Israel junction conditions for arbitrary spacetimes. This
has been used to obtain the surface energy density and the tangential pressure.
The minimal pressure provides the gateway to explore the expanding and
collapsing regions. We take Minkowski and Kantowski-Sachs spacetimes and use
the general formulation to investigate the expanding and collapsing regions of
the shell.
| [
{
"created": "Tue, 17 Aug 2010 02:30:38 GMT",
"version": "v1"
}
] | 2011-03-28 | [
[
"Sharif",
"M.",
""
],
[
"Abbas",
"G.",
""
]
] | We investigate the expanding and collapsing regions by taking two well-known spherically symmetric spacetimes. For this purpose, the general formalism is developed by using Israel junction conditions for arbitrary spacetimes. This has been used to obtain the surface energy density and the tangential pressure. The minimal pressure provides the gateway to explore the expanding and collapsing regions. We take Minkowski and Kantowski-Sachs spacetimes and use the general formulation to investigate the expanding and collapsing regions of the shell. |
1512.04566 | Tommaso De Lorenzo | Tommaso De Lorenzo and Alejandro Perez | Improved Black Hole Fireworks: Asymmetric Black-Hole-to-White-Hole
Tunneling Scenario | 18 Pages, 6 Figures | Phys. Rev. D 93, 124018 (2016) | 10.1103/PhysRevD.93.124018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new scenario for gravitational collapse has been recently proposed by
Haggard and Rovelli. Presenting the model under the name of black hole
fireworks, they claim that the accumulation of quantum gravitational effects
outside the horizon can cause the tunneling of geometry from a black hole to a
white hole, allowing a bounce of the collapsing star which can eventually go
back to infinity. In this paper we discuss the instabilities of this model and
propose a simple minimal modification which eliminates them, as well as other
related instabilities discussed in the literature. The new scenario is a
time-asymmetric version of the original model with a time-scale for the final
explosion that is shorter than m log m in Planck units. Our analysis highlights
the importance of irreversibility in gravitational collapse which, in turn,
uncovers important issues that cannot be addressed in detail without a full
quantum gravity treatment.
| [
{
"created": "Mon, 14 Dec 2015 21:34:03 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2016 15:29:04 GMT",
"version": "v2"
}
] | 2016-06-08 | [
[
"De Lorenzo",
"Tommaso",
""
],
[
"Perez",
"Alejandro",
""
]
] | A new scenario for gravitational collapse has been recently proposed by Haggard and Rovelli. Presenting the model under the name of black hole fireworks, they claim that the accumulation of quantum gravitational effects outside the horizon can cause the tunneling of geometry from a black hole to a white hole, allowing a bounce of the collapsing star which can eventually go back to infinity. In this paper we discuss the instabilities of this model and propose a simple minimal modification which eliminates them, as well as other related instabilities discussed in the literature. The new scenario is a time-asymmetric version of the original model with a time-scale for the final explosion that is shorter than m log m in Planck units. Our analysis highlights the importance of irreversibility in gravitational collapse which, in turn, uncovers important issues that cannot be addressed in detail without a full quantum gravity treatment. |
2403.11540 | Jo\~ao Lu\'is Rosa | Jo\~ao Lu\'is Rosa, Joaqu\'in Pelle, Daniela P\'erez | Accretion disks and relativistic line broadening in boson star
spacetimes | 13 pages, 7 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we analyze the observational properties of static, spherically
symmetric boson stars with fourth and sixth-order self-interactions, using the
Julia-based general-relativistic radiative transfer code Skylight. We assume
the boson stars are surrounded by an optically thick, geometrically thin
accretion disk. We use the Novikov-Thorne model to compute the energy flux,
introducing a physically based accretion model around these boson star
configurations. Additionally, we calculate the relativistic broadening of
emission lines, incorporating a lamppost corona model with full relativistic
effects for the first time around a boson star. Our results show distinct
observational features between quartic-potential boson stars and Schwarzschild
black holes, owing to the presence of stable circular orbits at all radii
around the former. On the other hand, compact solitonic boson stars, which
possess an innermost stable circular orbit, have observational features closely
similar to black holes. This similarity emphasizes their potential as
black-hole mimickers. However, the compact boson stars, lacking an event
horizon, have complex light-ring structures that produce potentially observable
differences from black holes with future generations of experiments.
| [
{
"created": "Mon, 18 Mar 2024 07:48:25 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Rosa",
"João Luís",
""
],
[
"Pelle",
"Joaquín",
""
],
[
"Pérez",
"Daniela",
""
]
] | In this work, we analyze the observational properties of static, spherically symmetric boson stars with fourth and sixth-order self-interactions, using the Julia-based general-relativistic radiative transfer code Skylight. We assume the boson stars are surrounded by an optically thick, geometrically thin accretion disk. We use the Novikov-Thorne model to compute the energy flux, introducing a physically based accretion model around these boson star configurations. Additionally, we calculate the relativistic broadening of emission lines, incorporating a lamppost corona model with full relativistic effects for the first time around a boson star. Our results show distinct observational features between quartic-potential boson stars and Schwarzschild black holes, owing to the presence of stable circular orbits at all radii around the former. On the other hand, compact solitonic boson stars, which possess an innermost stable circular orbit, have observational features closely similar to black holes. This similarity emphasizes their potential as black-hole mimickers. However, the compact boson stars, lacking an event horizon, have complex light-ring structures that produce potentially observable differences from black holes with future generations of experiments. |
2105.11623 | Adam D. Helfer | Adam D. Helfer | Center-of-mass ambiguity for Bondi-Metzner-Sachs charges | 7 pages. This is the Accepted Manuscript version of an article
accepted for publication in Classical and Quantum Gravity. IOP Publishing Ltd
is not responsible for any errors or omissions in this version of the
manuscript or any version derived from it. The Version of Record is available
online at 10.1088/1361-6382/abfc2e | Class. Quantum Grav. 38 (2021) 12LT01 | 10.1088/1361-6382/abfc2e | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Dray and Streubel proposed a definition of angular momentum in general
relativity based on `Bondi-Metzner-Sachs (BMS) charges'. I show here that the
natural definition of center of mass in this program has an
infinite-dimensional ambiguity. (This seems not to have been noticed before
because previous work has tacitly carried over a special-relativistic
assumption.) A related point is that the natural definition of spin in this
context is translation-, but not supertranslation-, invariant.
| [
{
"created": "Tue, 25 May 2021 02:39:22 GMT",
"version": "v1"
}
] | 2021-05-26 | [
[
"Helfer",
"Adam D.",
""
]
] | Dray and Streubel proposed a definition of angular momentum in general relativity based on `Bondi-Metzner-Sachs (BMS) charges'. I show here that the natural definition of center of mass in this program has an infinite-dimensional ambiguity. (This seems not to have been noticed before because previous work has tacitly carried over a special-relativistic assumption.) A related point is that the natural definition of spin in this context is translation-, but not supertranslation-, invariant. |
1205.6009 | Manuel Tiglio | Frank Herrmann, Scott E. Field, Chad R. Galley, Evan Ochsner, Manuel
Tiglio | Towards beating the curse of dimensionality for gravitational waves
using Reduced Basis | null | null | 10.1103/PhysRevD.86.084046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Reduced Basis approach, we efficiently compress and accurately
represent the space of waveforms for non-precessing binary black hole
inspirals, which constitutes a four dimensional parameter space (two masses,
two spin magnitudes). Compared to the non-spinning case, we find that only a
{\it marginal} increase in the (already relatively small) number of reduced
basis elements is required to represent any non-precessing waveform to nearly
numerical round-off precision. Most parameters selected by the algorithm are
near the boundary of the parameter space, leaving the bulk of its volume
sparse. Our results suggest that the full eight dimensional space (two masses,
two spin magnitudes, four spin orientation angles on the unit sphere) may be
highly compressible and represented with very high accuracy by a remarkably
small number of waveforms, thus providing some hope that the number of
numerical relativity simulations of binary black hole coalescences needed to
represent the entire space of configurations is not intractable. Finally, we
find that the {\it distribution} of selected parameters is robust to different
choices of seed values starting the algorithm, a property which should be
useful for indicating parameters for numerical relativity simulations of binary
black holes. In particular, we find that the mass ratios $m_1/m_2$ of
non-spinning binaries selected by the algorithm are mostly in the interval
$[1,3]$ and that the median of the distribution follows a power-law behavior
$\sim (m_1/m_2)^{-5.25}$.
| [
{
"created": "Sun, 27 May 2012 23:19:25 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Herrmann",
"Frank",
""
],
[
"Field",
"Scott E.",
""
],
[
"Galley",
"Chad R.",
""
],
[
"Ochsner",
"Evan",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Using the Reduced Basis approach, we efficiently compress and accurately represent the space of waveforms for non-precessing binary black hole inspirals, which constitutes a four dimensional parameter space (two masses, two spin magnitudes). Compared to the non-spinning case, we find that only a {\it marginal} increase in the (already relatively small) number of reduced basis elements is required to represent any non-precessing waveform to nearly numerical round-off precision. Most parameters selected by the algorithm are near the boundary of the parameter space, leaving the bulk of its volume sparse. Our results suggest that the full eight dimensional space (two masses, two spin magnitudes, four spin orientation angles on the unit sphere) may be highly compressible and represented with very high accuracy by a remarkably small number of waveforms, thus providing some hope that the number of numerical relativity simulations of binary black hole coalescences needed to represent the entire space of configurations is not intractable. Finally, we find that the {\it distribution} of selected parameters is robust to different choices of seed values starting the algorithm, a property which should be useful for indicating parameters for numerical relativity simulations of binary black holes. In particular, we find that the mass ratios $m_1/m_2$ of non-spinning binaries selected by the algorithm are mostly in the interval $[1,3]$ and that the median of the distribution follows a power-law behavior $\sim (m_1/m_2)^{-5.25}$. |
0907.4087 | Luca Lusanna | David Alba and Luca Lusanna | The Einstein-Maxwell-Particle System in the York Canonical Basis of ADM
Tetrad Gravity: I) The Equations of Motion in Arbitrary Schwinger Time Gauges | 108 pages. Revised version with improved presentation, rewriting of
Appendix A, inclusion of the explicit form of the Bianchi identity for the
energy-momentum tensor, corrected typos and update of references | null | null | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the coupling of N charged scalar particles plus the electro-magnetic
field to ADM tetrad gravity and its canonical formulation in asymptotically
Minkowskian space-times without super-translations. We make the canonical
transformation to the York canonical basis, where there is a separation between
the {\it inertial} (gauge) variables and the {\it tidal} ones inside the
gravitational field and a special role of the Eulerian observers associated to
the 3+1 splitting of space-time. The Dirac Hamiltonian is weakly equal to the
weak ADM energy. The Hamilton equations in Schwinger time gauges are given
explicitly. In the York basis they are naturally divided in four sets: a) the
contracted Bianchi identities; b) the equations for the inertial gauge
variables; c) the equations for the tidal ones; d) the equations for matter.
Finally we give the restriction of the Hamilton equations and of the
constraints to the family of {\it non-harmonic 3-orthogonal} gauges, in which
the instantaneous Riemannian 3-spaces have a diagonal 3-metric. The non-fixed
inertial gauge variable ${}^3K$ (the freedom in the clock synchronization
convention) gives rise to a negative kinetic term in the weak ADM energy
vanishing only in the gauges with ${}^3K = 0$: is it relevant for dark energy
and back-reaction? In the second paper there will be the linearization of the
theory to obtain Hamiltonian post-Minkowskian gravity with asymptotic Minkowski
background, non-flat instantaneous 3-spaces and no post-Newtonian expansion.
This will allow to explore the inertial effects induced by the York time
${}^3K$ in non-flat 3-spaces and to check how much dark matter can be explained
as an inertial aspect of Einstein's general relativity.
| [
{
"created": "Thu, 23 Jul 2009 14:48:21 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Dec 2009 11:33:53 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Sep 2010 13:53:56 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Apr 2011 12:42:05 GMT",
"version": "v4"
}
] | 2011-04-27 | [
[
"Alba",
"David",
""
],
[
"Lusanna",
"Luca",
""
]
] | We study the coupling of N charged scalar particles plus the electro-magnetic field to ADM tetrad gravity and its canonical formulation in asymptotically Minkowskian space-times without super-translations. We make the canonical transformation to the York canonical basis, where there is a separation between the {\it inertial} (gauge) variables and the {\it tidal} ones inside the gravitational field and a special role of the Eulerian observers associated to the 3+1 splitting of space-time. The Dirac Hamiltonian is weakly equal to the weak ADM energy. The Hamilton equations in Schwinger time gauges are given explicitly. In the York basis they are naturally divided in four sets: a) the contracted Bianchi identities; b) the equations for the inertial gauge variables; c) the equations for the tidal ones; d) the equations for matter. Finally we give the restriction of the Hamilton equations and of the constraints to the family of {\it non-harmonic 3-orthogonal} gauges, in which the instantaneous Riemannian 3-spaces have a diagonal 3-metric. The non-fixed inertial gauge variable ${}^3K$ (the freedom in the clock synchronization convention) gives rise to a negative kinetic term in the weak ADM energy vanishing only in the gauges with ${}^3K = 0$: is it relevant for dark energy and back-reaction? In the second paper there will be the linearization of the theory to obtain Hamiltonian post-Minkowskian gravity with asymptotic Minkowski background, non-flat instantaneous 3-spaces and no post-Newtonian expansion. This will allow to explore the inertial effects induced by the York time ${}^3K$ in non-flat 3-spaces and to check how much dark matter can be explained as an inertial aspect of Einstein's general relativity. |
gr-qc/9505013 | Kiyoshi Kamimura | Takeshi FUKUYAMA, Kiyoshi Kamimura, Songju YU | Toda Lattice and Tomimatsu-Sato Solutions | LaTeX 8 pages | J.Phys.Soc.Jap. 64 (1995) 3201-3206 | 10.1143/JPSJ.64.3201 | Rits-TH-9511, TOHO-FP-9551 | gr-qc | null | We discuss an analytic proof of a conjecture (Nakamura) that solutions of
Toda molecule equation give those of Ernst equation giving Tomimatsu-Sato
solutions of Einstein equation. Using Pfaffian identities it is shown for Weyl
solutions completely and for generic cases partially.
| [
{
"created": "Thu, 11 May 1995 02:47:49 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"FUKUYAMA",
"Takeshi",
""
],
[
"Kamimura",
"Kiyoshi",
""
],
[
"YU",
"Songju",
""
]
] | We discuss an analytic proof of a conjecture (Nakamura) that solutions of Toda molecule equation give those of Ernst equation giving Tomimatsu-Sato solutions of Einstein equation. Using Pfaffian identities it is shown for Weyl solutions completely and for generic cases partially. |
2203.02924 | Gui-Rong Liang | Haiyuan Feng (1), Miao Li (1), Gui-Rong Liang (1) and Rong-Jia Yang
(2) ((1) Department of Physics, Southern University of Science and
Technology, (2) College of Physical Science and Technology, Hebei University) | Adiabatic accretion onto black holes in Einstein-Maxwell-scalar theory | 17 pages, 4 figures | null | 10.1088/1475-7516/2022/04/027 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We study the adiabatic accretion process of ordinary baryonic gas onto
spherically symmetric black holes in Einstein-Maxwell-scalar theory, with two
parameters $\alpha$ and $\beta$ in the coupling term. Especially, we
demonstrate the range of the transonic points in terms of the charge-to-mass
ratio squared and the dimensionless coordinate radius, in two important classes
of black holes as examples. Further, we find that the two coupling parameters
give modifications to the mass accretion rate at different orders of the sound
speed at infinity. We also present their different effects on the temperature
ratios of the accreted gas.
| [
{
"created": "Sun, 6 Mar 2022 09:53:48 GMT",
"version": "v1"
}
] | 2022-04-27 | [
[
"Feng",
"Haiyuan",
""
],
[
"Li",
"Miao",
""
],
[
"Liang",
"Gui-Rong",
""
],
[
"Yang",
"Rong-Jia",
""
]
] | We study the adiabatic accretion process of ordinary baryonic gas onto spherically symmetric black holes in Einstein-Maxwell-scalar theory, with two parameters $\alpha$ and $\beta$ in the coupling term. Especially, we demonstrate the range of the transonic points in terms of the charge-to-mass ratio squared and the dimensionless coordinate radius, in two important classes of black holes as examples. Further, we find that the two coupling parameters give modifications to the mass accretion rate at different orders of the sound speed at infinity. We also present their different effects on the temperature ratios of the accreted gas. |
1611.00809 | Michael Good | Michael R.R. Good, Khalykbek Yelshibekov, Yen Chin Ong | On Horizonless Temperature with an Accelerating Mirror | 25 pages, 12 figures, v2 closely resembles the published version | J. High Energ. Phys. (2017) 2017: 13 | 10.1007/JHEP03(2017)013 | NORDITA-2016-115 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new solution of a unitary moving mirror is found to produce finite energy
and emit thermal radiation despite the absence of an acceleration horizon. In
the limit that the mirror approaches the speed of light, the model corresponds
to a black hole formed from the collapse of a null shell. For speeds less than
light, the black hole correspondence, if it exists, is that of a remnant.
| [
{
"created": "Mon, 31 Oct 2016 05:28:00 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2017 11:06:29 GMT",
"version": "v2"
}
] | 2017-03-07 | [
[
"Good",
"Michael R. R.",
""
],
[
"Yelshibekov",
"Khalykbek",
""
],
[
"Ong",
"Yen Chin",
""
]
] | A new solution of a unitary moving mirror is found to produce finite energy and emit thermal radiation despite the absence of an acceleration horizon. In the limit that the mirror approaches the speed of light, the model corresponds to a black hole formed from the collapse of a null shell. For speeds less than light, the black hole correspondence, if it exists, is that of a remnant. |
2309.08350 | Marek Rogatko | Marek Rogatko | Uniqueness of dark matter magnetized static black hole spacetime | 23 pages, RevTEx, to be published in Phys.Rev.D15 | null | 10.1103/PhysRevD.108.064026 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Uniqueness problem of static axially symmetric black hole in magnetic
Universe filled with {\it dark matter} component has been considered. The {\it
dark matter} model comprises the additional $U(1)$-gauge field ({\it dark
photon}) interacting with Maxwell one by the kinetic mixing term. We show that
all the solutions of Einstein-Maxwell {\it dark photon} gravity subject to the
same boundary and regularity conditions authorize the only static axially
symmetric black hole solutions with non-vanishing time and azimuthal components
of Maxwell and {\it hidden} sector gauge fields, say Schwarzschild-like black
hole immersed in {\it dark matter} Melvin Universe.
| [
{
"created": "Fri, 15 Sep 2023 12:17:37 GMT",
"version": "v1"
}
] | 2023-09-18 | [
[
"Rogatko",
"Marek",
""
]
] | Uniqueness problem of static axially symmetric black hole in magnetic Universe filled with {\it dark matter} component has been considered. The {\it dark matter} model comprises the additional $U(1)$-gauge field ({\it dark photon}) interacting with Maxwell one by the kinetic mixing term. We show that all the solutions of Einstein-Maxwell {\it dark photon} gravity subject to the same boundary and regularity conditions authorize the only static axially symmetric black hole solutions with non-vanishing time and azimuthal components of Maxwell and {\it hidden} sector gauge fields, say Schwarzschild-like black hole immersed in {\it dark matter} Melvin Universe. |
1110.4257 | Mohammad Nouri-Zonoz | B. Nazari and M. Nouri-Zonoz | Electromagnetic Casimir effect and the spacetime index of refraction | 16 pages, REVTeX 4, Replaced with the published version | Phys. Rev. D 85, 044060 (2012) | 10.1103/PhysRevD.85.044060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In [5] we investigated the response of vacuum energy to a gravitational field
by considering a Casimir apparatus in a weak gravitational field. Our approach
was based on a conjecture involving the interpretation of spacetime as a
refractive medium and its effect on vacuum energy composed of virtual massless
scalar particles. There it was shown how the case of virtual photons as the
constituents of vacuum could be inferred from that of the massless scalar
field. Here we explicitly show how the same conjecture applies to the
electromagnetic vacuum composed of virtual photons. Specifically we show that
the boundary conditions imposed on the components of the vector field,
decomposed into two scalar fields, result in the same frequency shift for
photons. Using the same decomposition and employing our conjecture, we also
calculate the electromagnetic energy density for the Casimir apparatus in a
weak gravitational field.
| [
{
"created": "Wed, 19 Oct 2011 12:20:56 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Feb 2012 13:50:42 GMT",
"version": "v2"
}
] | 2012-03-01 | [
[
"Nazari",
"B.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | In [5] we investigated the response of vacuum energy to a gravitational field by considering a Casimir apparatus in a weak gravitational field. Our approach was based on a conjecture involving the interpretation of spacetime as a refractive medium and its effect on vacuum energy composed of virtual massless scalar particles. There it was shown how the case of virtual photons as the constituents of vacuum could be inferred from that of the massless scalar field. Here we explicitly show how the same conjecture applies to the electromagnetic vacuum composed of virtual photons. Specifically we show that the boundary conditions imposed on the components of the vector field, decomposed into two scalar fields, result in the same frequency shift for photons. Using the same decomposition and employing our conjecture, we also calculate the electromagnetic energy density for the Casimir apparatus in a weak gravitational field. |
2210.09663 | Stefan Czimek | Stefan Czimek, Igor Rodnianski | Obstruction-free gluing for the Einstein equations | 81 pages, 5 figures | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we develop a new approach to the gluing problem in General
Relativity, that is, the problem of matching two solutions of the Einstein
equations along a spacelike or characteristic (null) hypersurface. In contrast
to the previous constructions, the new perspective actively utilizes the
nonlinearity of the constraint equations. As a result, we are able to remove
the $10$-dimensional spaces of obstructions to the null and spacelike
(asymptotically flat) gluing problems, previously known in the literature. In
particular, we show that any asymptotically flat spacelike initial data can be
glued to the Schwarzschild initial data of mass $M$ for any $M>0$ sufficiently
large. More generally, compared to the celebrated result of Corvino-Schoen, our
methods allow us to choose ourselves the Kerr spacelike initial data that is
being glued onto. As in our earlier work, our primary focus is the analysis of
the null problem, where we develop a new technique of combining low-frequency
linear analysis with high-frequency nonlinear control. The corresponding
spacelike results are derived a posteriori by solving a characteristic initial
value problem.
| [
{
"created": "Tue, 18 Oct 2022 08:03:33 GMT",
"version": "v1"
}
] | 2022-10-19 | [
[
"Czimek",
"Stefan",
""
],
[
"Rodnianski",
"Igor",
""
]
] | In this paper we develop a new approach to the gluing problem in General Relativity, that is, the problem of matching two solutions of the Einstein equations along a spacelike or characteristic (null) hypersurface. In contrast to the previous constructions, the new perspective actively utilizes the nonlinearity of the constraint equations. As a result, we are able to remove the $10$-dimensional spaces of obstructions to the null and spacelike (asymptotically flat) gluing problems, previously known in the literature. In particular, we show that any asymptotically flat spacelike initial data can be glued to the Schwarzschild initial data of mass $M$ for any $M>0$ sufficiently large. More generally, compared to the celebrated result of Corvino-Schoen, our methods allow us to choose ourselves the Kerr spacelike initial data that is being glued onto. As in our earlier work, our primary focus is the analysis of the null problem, where we develop a new technique of combining low-frequency linear analysis with high-frequency nonlinear control. The corresponding spacelike results are derived a posteriori by solving a characteristic initial value problem. |
1811.00831 | Natalia Kharuk | N.V. Kharuk, S.N. Manida, S.A. Paston, A.A. Sheykin | Modifying the theory of gravity by changing independent variables | LaTeX, 6 pages, based on a talk given at the XXth International
Seminar on High Energy Physics (QUARKS-2018), Valday, Russia, May 27 - June
2, 2018 | EPJ Web of Conferences 191, 07007 (2018) | 10.1051/epjconf/201819107007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some particular modifications of gravity in search for a natural way
to unify the gravitational and electromagnetic interaction. The certain
components of connection in the appearing variants of the theory can be
identified with electromagnetic potential. The methods of adding matter in the
form of scalar and spinor fields are studied. In particular, the expansion of
the local symmetry group up to $GL(2,C)$ is explored, in which equations of
Einstein, Maxwell and Dirac are reproduced for the theory with Weyl spinor.
| [
{
"created": "Fri, 2 Nov 2018 12:17:52 GMT",
"version": "v1"
}
] | 2018-11-05 | [
[
"Kharuk",
"N. V.",
""
],
[
"Manida",
"S. N.",
""
],
[
"Paston",
"S. A.",
""
],
[
"Sheykin",
"A. A.",
""
]
] | We study some particular modifications of gravity in search for a natural way to unify the gravitational and electromagnetic interaction. The certain components of connection in the appearing variants of the theory can be identified with electromagnetic potential. The methods of adding matter in the form of scalar and spinor fields are studied. In particular, the expansion of the local symmetry group up to $GL(2,C)$ is explored, in which equations of Einstein, Maxwell and Dirac are reproduced for the theory with Weyl spinor. |
1006.3327 | Owen Pavel Fernandez Piedra | Owen Pavel Fern\'andez Piedra | Gravitino perturbations in Schwarzschild black holes | null | Int.J.Mod.Phys.D20:93-109,2011 | 10.1142/S0218271811018676 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the time evolution of massless gravitino perturbations in
Schwarzschild black holes, and show that as in the case of fields of other
values of spin, the evolution comes in three stages, after an initial outburst
as a first stage, we observe the damped oscillations characteristic of the
quasinormal ringing stage, followed by long time tails. Using the sixth order
WKB method and Prony fitting of time domain data we determine the quasinormal
frequencies. There is a good correspondence between the results obtained by the
above two methods, and we obtain a considerable improvement with respect to the
previously obtained third order WKB results. We also show that the response of
a black hole depends crucially on the spin class of the perturbing field: the
quality factor becomes a decreasing function of the spin for boson
perturbations, whereas the opposite situation appears for fermion ones.
| [
{
"created": "Wed, 16 Jun 2010 21:10:15 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Jul 2010 17:23:17 GMT",
"version": "v2"
}
] | 2011-02-09 | [
[
"Piedra",
"Owen Pavel Fernández",
""
]
] | We consider the time evolution of massless gravitino perturbations in Schwarzschild black holes, and show that as in the case of fields of other values of spin, the evolution comes in three stages, after an initial outburst as a first stage, we observe the damped oscillations characteristic of the quasinormal ringing stage, followed by long time tails. Using the sixth order WKB method and Prony fitting of time domain data we determine the quasinormal frequencies. There is a good correspondence between the results obtained by the above two methods, and we obtain a considerable improvement with respect to the previously obtained third order WKB results. We also show that the response of a black hole depends crucially on the spin class of the perturbing field: the quality factor becomes a decreasing function of the spin for boson perturbations, whereas the opposite situation appears for fermion ones. |
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