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1012.2456 | Sebastiano Bernuzzi | Sebastiano Bernuzzi, Alessandro Nagar and Anil Zenginoglu | Binary black hole coalescence in the extreme-mass-ratio limit: testing
and improving the effective-one-body multipolar waveform | null | Phys.Rev.D83:064010,2011 | 10.1103/PhysRevD.83.064010 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the properties of the effective-one-body (EOB) multipolar
gravitational waveform emitted by nonspinning black-hole binaries of masses
$\mu$ and $M$ in the extreme-mass-ratio limit, $\mu/M=\nu\ll 1$. We focus on
the transition from quasicircular inspiral to plunge, merger and ringdown.We
compare the EOB waveform to a Regge-Wheeler-Zerilli (RWZ) waveform computed
using the hyperboloidal layer method and extracted at null infinity. Because
the EOB waveform keeps track analytically of most phase differences in the
early inspiral, we do not allow for any arbitrary time or phase shift between
the waveforms. The dynamics of the particle, common to both wave-generation
formalisms, is driven by leading-order ${\cal O}(\nu)$ analytically--resummed
radiation reaction. The EOB and the RWZ waveforms have an initial dephasing of
about $5\times 10^{-4}$ rad and maintain then a remarkably accurate phase
coherence during the long inspiral ($\sim 33$ orbits), accumulating only about
$-2\times 10^{-3}$ rad until the last stable orbit, i.e. $\Delta\phi/\phi\sim
-5.95\times 10^{-6}$. We obtain such accuracy without calibrating the
analytically-resummed EOB waveform to numerical data, which indicates the
aptitude of the EOB waveform for LISA-oriented studies. We then improve the
behavior of the EOB waveform around merger by introducing and tuning
next-to-quasi-circular corrections both in the gravitational wave amplitude and
phase. For each multipole we tune only four next-to-quasi-circular parameters
by requiring compatibility between EOB and RWZ waveforms at the light-ring. The
resulting phase difference around merger time is as small as $\pm 0.015$ rad,
with a fractional amplitude agreement of 2.5%. This suggest that
next-to-quasi-circular corrections to the phase can be a useful ingredient in
comparisons between EOB and numerical relativity waveforms.
| [
{
"created": "Sat, 11 Dec 2010 13:34:26 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Mar 2011 19:13:58 GMT",
"version": "v2"
}
] | 2011-03-22 | [
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Zenginoglu",
"Anil",
""
]
] | We discuss the properties of the effective-one-body (EOB) multipolar gravitational waveform emitted by nonspinning black-hole binaries of masses $\mu$ and $M$ in the extreme-mass-ratio limit, $\mu/M=\nu\ll 1$. We focus on the transition from quasicircular inspiral to plunge, merger and ringdown.We compare the EOB waveform to a Regge-Wheeler-Zerilli (RWZ) waveform computed using the hyperboloidal layer method and extracted at null infinity. Because the EOB waveform keeps track analytically of most phase differences in the early inspiral, we do not allow for any arbitrary time or phase shift between the waveforms. The dynamics of the particle, common to both wave-generation formalisms, is driven by leading-order ${\cal O}(\nu)$ analytically--resummed radiation reaction. The EOB and the RWZ waveforms have an initial dephasing of about $5\times 10^{-4}$ rad and maintain then a remarkably accurate phase coherence during the long inspiral ($\sim 33$ orbits), accumulating only about $-2\times 10^{-3}$ rad until the last stable orbit, i.e. $\Delta\phi/\phi\sim -5.95\times 10^{-6}$. We obtain such accuracy without calibrating the analytically-resummed EOB waveform to numerical data, which indicates the aptitude of the EOB waveform for LISA-oriented studies. We then improve the behavior of the EOB waveform around merger by introducing and tuning next-to-quasi-circular corrections both in the gravitational wave amplitude and phase. For each multipole we tune only four next-to-quasi-circular parameters by requiring compatibility between EOB and RWZ waveforms at the light-ring. The resulting phase difference around merger time is as small as $\pm 0.015$ rad, with a fractional amplitude agreement of 2.5%. This suggest that next-to-quasi-circular corrections to the phase can be a useful ingredient in comparisons between EOB and numerical relativity waveforms. |
2405.15878 | Ankur Barsode | A. Barsode, S. J. Kapadia, P. Ajith | Constraints on compact dark matter from the non-observation of
gravitational-wave strong lensing | 8 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We use the non-observation of strong lensing of gravitational waves (GWs) in
the first three observation runs of LIGO-Virgo detectors to constrain the
fraction of dark matter in the form of compact objects in the mass range
$10^{6}-10^{9}~{\mathrm{M}_\odot}$. Using a Bayesian formalism supplemented by
astrophysical simulations of strong lensing of GWs, we constrain the compact
dark matter fraction to $\lesssim 0.4-0.6$ with currently available data and
show that they may get significantly tighter in the future. We find that
multiple lensing -- i.e., GWs getting deflected by multiple compact objects on
their way to us -- is possible. By ignoring this, we underestimate the
constraints by a few percent.
| [
{
"created": "Fri, 24 May 2024 18:42:23 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Barsode",
"A.",
""
],
[
"Kapadia",
"S. J.",
""
],
[
"Ajith",
"P.",
""
]
] | We use the non-observation of strong lensing of gravitational waves (GWs) in the first three observation runs of LIGO-Virgo detectors to constrain the fraction of dark matter in the form of compact objects in the mass range $10^{6}-10^{9}~{\mathrm{M}_\odot}$. Using a Bayesian formalism supplemented by astrophysical simulations of strong lensing of GWs, we constrain the compact dark matter fraction to $\lesssim 0.4-0.6$ with currently available data and show that they may get significantly tighter in the future. We find that multiple lensing -- i.e., GWs getting deflected by multiple compact objects on their way to us -- is possible. By ignoring this, we underestimate the constraints by a few percent. |
0803.2508 | Roberto Chan | R. Chan, M. F. A. da Silva, J. F. Villas da Rocha | On Anisotropic Dark Energy | 15 pages, 1 figure, Abstract and Introduction changed, references
added, corrected typos, accepted for publication in MPLA | Mod.Phys.Lett.A24:1137-1146,2009 | 10.1142/S0217732309028692 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the discovery of the accelerated expansion of the universe, it was
necessary to introduce a new component of matter distribution called dark
energy. The standard cosmological model considers isotropy of the pressure and
assumes an equation of state $p=\omega \rho$, relating the pressure $p$ and the
energy density $\rho$. The interval of the parameter $\omega$ defines the kind
of matter of the universe, related to the fulfillment, or not, of the energy
conditions of the fluid. The recent interest in this kind of fluid with
anisotropic pressure, in the scenario of the gravitational collapse and star
formation, imposes a carefull analysis of the energy conditions and the role of
the components of the pressure. Here, in this work, we show an example where
the classification of dark energy for isotropic pressure fluids is used
incorrectly for anisotropic fluids. The correct classification and its
consequences are presented.
| [
{
"created": "Mon, 17 Mar 2008 19:20:21 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Sep 2008 14:01:42 GMT",
"version": "v2"
}
] | 2012-10-25 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"da Rocha",
"J. F. Villas",
""
]
] | Since the discovery of the accelerated expansion of the universe, it was necessary to introduce a new component of matter distribution called dark energy. The standard cosmological model considers isotropy of the pressure and assumes an equation of state $p=\omega \rho$, relating the pressure $p$ and the energy density $\rho$. The interval of the parameter $\omega$ defines the kind of matter of the universe, related to the fulfillment, or not, of the energy conditions of the fluid. The recent interest in this kind of fluid with anisotropic pressure, in the scenario of the gravitational collapse and star formation, imposes a carefull analysis of the energy conditions and the role of the components of the pressure. Here, in this work, we show an example where the classification of dark energy for isotropic pressure fluids is used incorrectly for anisotropic fluids. The correct classification and its consequences are presented. |
0910.5751 | Aron Wall | Aron C. Wall | Proving the Achronal Averaged Null Energy Condition from the Generalized
Second Law | 19 pages, 1 figure. Added 2 paragraphs to end of section 2 | Phys.Rev.D81:024038,2010 | 10.1103/PhysRevD.81.024038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A null line is a complete achronal null geodesic. It is proven that for any
quantum fields minimally coupled to semiclassical Einstein gravity, the
averaged null energy condition (ANEC) on null lines is a consequence of the
generalized second law of thermodynamics for causal horizons. Auxiliary
assumptions include CPT and the existence of a suitable renormalization scheme
for the generalized entropy.
Although the ANEC can be violated on general geodesics in curved spacetimes,
as long as the ANEC holds on null lines there exist theorems showing that
semiclassical gravity should satisfy positivity of energy, topological
censorship, and should not admit closed timelike curves. It is pointed out that
these theorems fail once the linearized graviton field is quantized, because
then the renormalized shear squared term in the Raychaudhuri equation can be
negative. A "shear-inclusive" generalization of the ANEC is proposed to remedy
this, and is proven under an additional assumption about perturbations to
horizons in classical general relativity.
| [
{
"created": "Thu, 29 Oct 2009 23:43:08 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2010 01:57:35 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Wall",
"Aron C.",
""
]
] | A null line is a complete achronal null geodesic. It is proven that for any quantum fields minimally coupled to semiclassical Einstein gravity, the averaged null energy condition (ANEC) on null lines is a consequence of the generalized second law of thermodynamics for causal horizons. Auxiliary assumptions include CPT and the existence of a suitable renormalization scheme for the generalized entropy. Although the ANEC can be violated on general geodesics in curved spacetimes, as long as the ANEC holds on null lines there exist theorems showing that semiclassical gravity should satisfy positivity of energy, topological censorship, and should not admit closed timelike curves. It is pointed out that these theorems fail once the linearized graviton field is quantized, because then the renormalized shear squared term in the Raychaudhuri equation can be negative. A "shear-inclusive" generalization of the ANEC is proposed to remedy this, and is proven under an additional assumption about perturbations to horizons in classical general relativity. |
2305.04011 | Spiros Cotsakis | Spiros Cotsakis, Jose P. Mimoso, John Miritzis | Legendre scalarization in gravity and cosmology | v2: 14 pages, 3 figures, matches published version | Eur. Phys. J. C (2023) 83:433 | 10.1140/epjc/s10052-023-11628-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new formulation of $f(R)$ gravity, dubbed scalarized $f(R)$
gravity, in which the Legendre transform is included as a dynamical term. This
leads to a theory with second-order field equations that describes general
relativity with a self-interacting scalar field, without requiring the
introduction of conformal frames. We demonstrate that the quadratic version of
scalarized $f(R)$ gravity reduces to general relativity with a massive scalar
field, and we explore its implications for Friedmann cosmology. Our findings
suggest that scalarized $f(R)$ gravity may lead to simplified descriptions of
cosmological applications, while the proposed formulation could offer a new
perspective on the relationship between $f(R)$ gravity and scalar-tensor
theories.
| [
{
"created": "Sat, 6 May 2023 10:52:00 GMT",
"version": "v1"
},
{
"created": "Sat, 27 May 2023 06:24:07 GMT",
"version": "v2"
}
] | 2023-06-07 | [
[
"Cotsakis",
"Spiros",
""
],
[
"Mimoso",
"Jose P.",
""
],
[
"Miritzis",
"John",
""
]
] | We propose a new formulation of $f(R)$ gravity, dubbed scalarized $f(R)$ gravity, in which the Legendre transform is included as a dynamical term. This leads to a theory with second-order field equations that describes general relativity with a self-interacting scalar field, without requiring the introduction of conformal frames. We demonstrate that the quadratic version of scalarized $f(R)$ gravity reduces to general relativity with a massive scalar field, and we explore its implications for Friedmann cosmology. Our findings suggest that scalarized $f(R)$ gravity may lead to simplified descriptions of cosmological applications, while the proposed formulation could offer a new perspective on the relationship between $f(R)$ gravity and scalar-tensor theories. |
1602.03840 | LVC Publications | The LIGO Scientific Collaboration and the Virgo Collaboration: The
LIGO Scientific Collaboration and the Virgo Collaboration: B. P. Abbott, R.
Abbott, T. D. Abbott, M. R. Abernathy, F. Acernese, K. Ackley, C. Adams, T.
Adams, P. Addesso, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K.
Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, B. Allen,
A. Allocca, P. A. Altin, S. B. Anderson, W. G. Anderson, K. Arai, M. C.
Araya, C. C. Arceneaux, J. S. Areeda, N. Arnaud, K. G. Arun, S. Ascenzi, G.
Ashton, M. Ast, S. M. Aston, P. Astone, P. Aufmuth, C. Aulbert, S. Babak, P.
Bacon, M. K. M. Bader, P. T. Baker, F. Baldaccini, G. Ballardin, S. W.
Ballmer, J. C. Barayoga, S. E. Barclay, B. C. Barish, D. Barker, F. Barone,
B. Barr, L. Barsotti, M. Barsuglia, D. Barta, J. Bartlett, I. Bartos, R.
Bassiri, A. Basti, J. C. Batch, C. Baune, V. Bavigadda, M. Bazzan, B. Behnke,
M. Bejger, A. S. Bell, C. J. Bell, B. K. Berger, J. Bergman, G. Bergmann, C.
P. L. Berry, D. Bersanetti, A. Bertolini, J. Betzwieser, S. Bhagwat, R.
Bhandare, I. A. Bilenko, G. Billingsley, J. Birch, R. Birney, O. Birnholtz,
S. Biscans, A. Bisht, M. Bitossi, C. Biwer, M. A. Bizouard, J. K. Blackburn,
C. D. Blair, D. G. Blair, R. M. Blair, S. Bloemen, O. Bock, T. P. Bodiya, M.
Boer, G. Bogaert, C. Bogan, A. Bohe, P. Bojtos, C. Bond, F. Bondu, R.
Bonnand, B. A. Boom, R. Bork, V. Boschi, S. Bose, Y. Bouffanais, A. Bozzi, C.
Bradaschia, P. R. Brady, V. B. Braginsky, M. Branchesi, J. E. Brau, T.
Briant, A. Brillet, M. Brinkmann, V. Brisson, P. Brockill, A. F. Brooks, D.
A. Brown, D. D. Brown, N. M. Brown, C. C. Buchanan, A. Buikema, T. Bulik, H.
J. Bulten, A. Buonanno, D. Buskulic, C. Buy, R. L. Byer, L. Cadonati, G.
Cagnoli, C. Cahillane, J. Calder\'on Bustillo, T. Callister, E. Calloni, J.
B. Camp, K. C. Cannon, J. Cao, C. D. Capano, E. Capocasa, F. Carbognani, S.
Caride, J. Casanueva Diaz, C. Casentini, S. Caudill, M. Cavagli\`a, F.
Cavalier, R. Cavalieri, G. Cella, C. B. Cepeda, L. Cerboni Baiardi, G.
Cerretani, E. Cesarini, R. Chakraborty, T. Chalermsongsak, S. J. Chamberlin,
M. Chan, S. Chao, P. Charlton, E. Chassande-Mottin, H. Y. Chen, Y. Chen, C.
Cheng, A. Chincarini, A. Chiummo, H. S. Cho, M. Cho, J. H. Chow, N.
Christensen, Q. Chu, S. Chua, S. Chung, G. Ciani, F. Clara, J. A. Clark, F.
Cleva, E. Coccia, P.-F. Cohadon, A. Colla, C. G. Collette, L. Cominsky, M.
Constancio Jr., A. Conte, L. Conti, D. Cook, T. R. Corbitt, N. Cornish, A.
Corsi, S. Cortese, C. A. Costa, M. W. Coughlin, S. B. Coughlin, J.-P. Coulon,
S. T. Countryman, P. Couvares, E. E. Cowan, D. M. Coward, M. J. Cowart, D. C.
Coyne, R. Coyne, K. Craig, J. D. E. Creighton, J. Cripe, S. G. Crowder, A.
Cumming, L. Cunningham, E. Cuoco, T. Dal Canton, S. L. Danilishin, S.
D\'Antonio, K. Danzmann, N. S. Darman, V. Dattilo, I. Dave, H. P. Daveloza,
M. Davier, G. S. Davies, E. J. Daw, R. Day, D. DeBra, G. Debreczeni, J.
Degallaix, M. De Laurentis, S. Del\'eglise, W. Del Pozzo, T. Denker, T. Dent,
H. Dereli, V. Dergachev, R. De Rosa, R. T. DeRosa, R. DeSalvo, C. Devine, S.
Dhurandhar, M. C. D\'iaz, L. Di Fiore, M. Di Giovanni, A. Di Lieto, S. Di
Pace, I. Di Palma, A. Di Virgilio, G. Dojcinoski, V. Dolique, F. Donovan, K.
L. Dooley, S. Doravari, R. Douglas, T. P. Downes, M. Drago, R. W. P. Drever,
J. C. Driggers, Z. Du, M. Ducrot, S. E. Dwyer, T. B. Edo, M. C. Edwards, A.
Effler, H.-B. Eggenstein, P. Ehrens, J. Eichholz, S. S. Eikenberry, W.
Engels, R. C. Essick, Z. Etienne, T. Etzel, M. Evans, T. M. Evans, R.
Everett, M. Factourovich, V. Fafone, H. Fair, S. Fairhurst, X. Fan, Q. Fang,
S. Farinon, B. Farr, W. M. Farr, E. Fauchon-Jones, M. Favata, M. Fays, H.
Fehrmann, M. M. Fejer, I. Ferrante, E. C. Ferreira, F. Ferrini, F. Fidecaro,
I. Fiori, D. Fiorucci, R. P. Fisher, R. Flaminio, M. Fletcher, J.-D.
Fournier, S. Franco, S. Frasca, F. Frasconi, Z. Frei, A. Freise, R. Frey, V.
Frey, T. T. Fricke, P. Fritschel, V. V. Frolov, P. Fulda, M. Fyffe, H. A. G.
Gabbard, S. M. Gaebel, J. R. Gair, L. Gammaitoni, S. G. Gaonkar, F. Garufi,
A. Gatto, G. Gaur, N. Gehrels, G. Gemme, B. Gendre, E. Genin, A. Gennai, J.
George, L. Gergely, V. Germain, Archisman Ghosh, S. Ghosh, J. A. Giaime, K.
D. Giardina, A. Giazotto, K. Gill, A. Glaefke, E. Goetz, R. Goetz, L. Gondan,
G. Gonz\'alez, J. M. Gonzalez Castro, A. Gopakumar, N. A. Gordon, M. L.
Gorodetsky, S. E. Gossan, M. Gosselin, R. Gouaty, C. Graef, P. B. Graff, M.
Granata, A. Grant, S. Gras, C. Gray, G. Greco, A. C. Green, P. Groot, H.
Grote, S. Grunewald, G. M. Guidi, X. Guo, A. Gupta, M. K. Gupta, K. E.
Gushwa, E. K. Gustafson, R. Gustafson, J. J. Hacker, B. R. Hall, E. D. Hall,
G. Hammond, M. Haney, M. M. Hanke, J. Hanks, C. Hanna, M. D. Hannam, J.
Hanson, T. Hardwick, J. Harms, G. M. Harry, I. W. Harry, M. J. Hart, M. T.
Hartman, C.-J. Haster, K. Haughian, J. Healy, A. Heidmann, M. C. Heintze, H.
Heitmann, P. Hello, G. Hemming, M. Hendry, I. S. Heng, J. Hennig, A. W.
Heptonstall, M. Heurs, S. Hild, D. Hoak, K. A. Hodge, D. Hofman, S. E.
Hollitt, K. Holt, D. E. Holz, P. Hopkins, D. J. Hosken, J. Hough, E. A.
Houston, E. J. Howell, Y. M. Hu, S. Huang, E. A. Huerta, D. Huet, B. Hughey,
S. Husa, S. H. Huttner, T. Huynh-Dinh, A. Idrisy, N. Indik, D. R. Ingram, R.
Inta, H. N. Isa, J.-M. Isac, M. Isi, G. Islas, T. Isogai, B. R. Iyer, K.
Izumi, T. Jacqmin, H. Jang, K. Jani, P. Jaranowski, S. Jawahar, F.
Jim\'enez-Forteza, W. W. Johnson, N. K. Johnson-McDaniel, D. I. Jones, R.
Jones, R. J. G. Jonker, L. Ju, Haris K, C. V. Kalaghatgi, V. Kalogera, S.
Kandhasamy, G. Kang, J. B. Kanner, S. Karki, M. Kasprzack, E. Katsavounidis,
W. Katzman, S. Kaufer, T. Kaur, K. Kawabe, F. Kawazoe, F. K\'ef\'elian, M. S.
Kehl, D. Keitel, D. B. Kelley, W. Kells, R. Kennedy, J. S. Key, A.
Khalaidovski, F. Y. Khalili, I. Khan, S. Khan, Z. Khan, E. A. Khazanov, N.
Kijbunchoo, C. Kim, J. Kim, K. Kim, Nam-Gyu Kim, Namjun Kim, Y.-M. Kim, E. J.
King, P. J. King, D. L. Kinzel, J. S. Kissel, L. Kleybolte, S. Klimenko, S.
M. Koehlenbeck, K. Kokeyama, S. Koley, V. Kondrashov, A. Kontos, M. Korobko,
W. Z. Korth, I. Kowalska, D. B. Kozak, V. Kringel, B. Krishnan, A. Kr\'olak,
C. Krueger, G. Kuehn, P. Kumar, L. Kuo, A. Kutynia, B. D. Lackey, M. Landry,
J. Lange, B. Lantz, P. D. Lasky, A. Lazzarini, C. Lazzaro, P. Leaci, S.
Leavey, E. O. Lebigot, C. H. Lee, H. K. Lee, H. M. Lee, K. Lee, A. Lenon, M.
Leonardi, J. R. Leong, N. Leroy, N. Letendre, Y. Levin, B. M. Levine, T. G.
F. Li, A. Libson, T. B. Littenberg, N. A. Lockerbie, J. Logue, A. L.
Lombardi, L. T. London, J. E. Lord, M. Lorenzini, V. Loriette, M. Lormand, G.
Losurdo, J. D. Lough, C. O. Lousto, G. Lovelace, H. L\"uck, A. P. Lundgren,
J. Luo, R. Lynch, Y. Ma, T. MacDonald, B. Machenschalk, M. MacInnis, D. M.
Macleod, F. Maga\~na-Sandoval, R. M. Magee, M. Mageswaran, E. Majorana, I.
Maksimovic, V. Malvezzi, N. Man, I. Mandel, V. Mandic, V. Mangano, G. L.
Mansell, M. Manske, M. Mantovani, F. Marchesoni, F. Marion, S. M\'arka, Z.
M\'arka, A. S. Markosyan, E. Maros, F. Martelli, L. Martellini, I. W. Martin,
R. M. Martin, D. V. Martynov, J. N. Marx, K. Mason, A. Masserot, T. J.
Massinger, M. Masso-Reid, F. Matichard, L. Matone, N. Mavalvala, N. Mazumder,
G. Mazzolo, R. McCarthy, D. E. McClelland, S. McCormick, S. C. McGuire, G.
McIntyre, J. McIver, D. J. McManus, S. T. McWilliams, D. Meacher, G. D.
Meadors, J. Meidam, A. Melatos, G. Mendell, D. Mendoza-Gandara, R. A. Mercer,
E. Merilh, M. Merzougui, S. Meshkov, C. Messenger, C. Messick, P. M. Meyers,
F. Mezzani, H. Miao, C. Michel, H. Middleton, E. E. Mikhailov, L. Milano, J.
Miller, M. Millhouse, Y. Minenkov, J. Ming, S. Mirshekari, C. Mishra, S.
Mitra, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, A. Moggi, M. Mohan,
S. R. P. Mohapatra, M. Montani, B. C. Moore, C. J. Moore, D. Moraru, G.
Moreno, S. R. Morriss, K. Mossavi, B. Mours, C. M. Mow-Lowry, C. L. Mueller,
G. Mueller, A. W. Muir, Arunava Mukherjee, D. Mukherjee, S. Mukherjee, N.
Mukund, A. Mullavey, J. Munch, D. J. Murphy, P. G. Murray, A. Mytidis, I.
Nardecchia, L. Naticchioni, R. K. Nayak, V. Necula, K. Nedkova, G. Nelemans,
M. Neri, A. Neunzert, G. Newton, T. T. Nguyen, A. B. Nielsen, S. Nissanke, A.
Nitz, F. Nocera, D. Nolting, M. E. Normandin, L. K. Nuttall, J. Oberling, E.
Ochsner, J. O'Dell, E. Oelker, G. H. Ogin, J. J. Oh, S. H. Oh, F. Ohme, M.
Oliver, P. Oppermann, Richard J. Oram, B. O'Reilly, R. O'Shaughnessy, D. J.
Ottaway, R. S. Ottens, H. Overmier, B. J. Owen, A. Pai, S. A. Pai, J. R.
Palamos, O. Palashov, C. Palomba, A. Pal-Singh, H. Pan, Y. Pan, C. Pankow, F.
Pannarale, B. C. Pant, F. Paoletti, A. Paoli, M. A. Papa, H. R. Paris, W.
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L. Ward, J. Warner, M. Was, B. Weaver, L.-W. Wei, M. Weinert, A. J.
Weinstein, R. Weiss, T. Welborn, L. Wen, P. Wessels, T. Westphal, K. Wette,
J. T. Whelan, D. J. White, B. F. Whiting, R. D. Williams, A. R. Williamson,
J. L. Willis, B. Willke, M. H. Wimmer, W. Winkler, C. C. Wipf, H. Wittel, G.
Woan, J. Worden, J. L. Wright, G. Wu, J. Yablon, W. Yam, H. Yamamoto, C. C.
Yancey, M. J. Yap, H. Yu, M. Yvert, A. Zadro.zny, L. Zangrando, M. Zanolin,
J.-P. Zendri, M. Zevin, F. Zhang, L. Zhang, M. Zhang, Y. Zhang, C. Zhao, M.
Zhou, Z. Zhou, X. J. Zhu, M. E. Zucker, S. E. Zuraw, J. Zweizig and M. Boyle,
B. Br\"ugmann, M. Campanelli, M. Clark, D. A. Hemberger, L. E. Kidder, M.
Kinsey, P. Laguna, S. Ossokine, M. A. Scheel, B. Szilagyi, S. Teukolsky, Y.
Zlochower and M. Boyle, B. Br\"ugmann, M. Campanelli, M. Clark, D. A.
Hemberger, L. E. Kidder, M. Kinsey, P. Laguna, S. Ossokine, M. A. Scheel, B.
Szilagyi, S. Teukolsky, Y. Zlochower | Properties of the Binary Black Hole Merger GW150914 | 19 pages, 6 figures | Phys. Rev. Lett. 116, 241102 (2016) | 10.1103/PhysRevLett.116.241102 | LIGO-P1500218 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | On September 14, 2015, the Laser Interferometer Gravitational-wave
Observatory (LIGO) detected a gravitational-wave transient (GW150914); we
characterize the properties of the source and its parameters. The data around
the time of the event were analyzed coherently across the LIGO network using a
suite of accurate waveform models that describe gravitational waves from a
compact binary system in general relativity. GW150914 was produced by a nearly
equal mass binary black hole of $36^{+5}_{-4} M_\odot$ and $29^{+4}_{-4}
M_\odot$; for each parameter we report the median value and the range of the
90% credible interval. The dimensionless spin magnitude of the more massive
black hole is bound to be $<0.7$ (at 90% probability). The luminosity distance
to the source is $410^{+160}_{-180}$ Mpc, corresponding to a redshift
$0.09^{+0.03}_{-0.04}$ assuming standard cosmology. The source location is
constrained to an annulus section of $610$ deg$^2$, primarily in the southern
hemisphere. The binary merges into a black hole of $62^{+4}_{-4} M_\odot$ and
spin $0.67^{+0.05}_{-0.07}$. This black hole is significantly more massive than
any other inferred from electromagnetic observations in the stellar-mass
regime.
| [
{
"created": "Thu, 11 Feb 2016 19:26:47 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jun 2016 11:16:18 GMT",
"version": "v2"
}
] | 2016-06-21 | [
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] | On September 14, 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) detected a gravitational-wave transient (GW150914); we characterize the properties of the source and its parameters. The data around the time of the event were analyzed coherently across the LIGO network using a suite of accurate waveform models that describe gravitational waves from a compact binary system in general relativity. GW150914 was produced by a nearly equal mass binary black hole of $36^{+5}_{-4} M_\odot$ and $29^{+4}_{-4} M_\odot$; for each parameter we report the median value and the range of the 90% credible interval. The dimensionless spin magnitude of the more massive black hole is bound to be $<0.7$ (at 90% probability). The luminosity distance to the source is $410^{+160}_{-180}$ Mpc, corresponding to a redshift $0.09^{+0.03}_{-0.04}$ assuming standard cosmology. The source location is constrained to an annulus section of $610$ deg$^2$, primarily in the southern hemisphere. The binary merges into a black hole of $62^{+4}_{-4} M_\odot$ and spin $0.67^{+0.05}_{-0.07}$. This black hole is significantly more massive than any other inferred from electromagnetic observations in the stellar-mass regime. |
2107.12615 | Bin Wu | Chao Wang, Bin Wu, Zhen-Ming Xu, Wen-Li Yang | Ruppeiner Geometry of the RN-AdS Black Hole Using Shadow Formalism | 18 pages, 9 figures | Nucl.Phys.B 976 (2022) 115698 | 10.1016/j.nuclphysb.2022.115698 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The connection between the shadow radius and the Ruppeiner geometry of a
charged static spherically symmetric black hole is investigated. The normalized
curvature scalar is adopted, and its close relation to the Van der Waals-like
and Hawking-Page phase transition of Reissner-Nordstr\"{o}m AdS black hole is
studied. The results show that the shadow radius is a useful tool to reveal the
correct information of the phase structure and the underlying microstructure of
the black hole, which opens a new window to investigate the strong gravity
system from the observational point of view.
| [
{
"created": "Tue, 27 Jul 2021 06:02:19 GMT",
"version": "v1"
}
] | 2022-03-17 | [
[
"Wang",
"Chao",
""
],
[
"Wu",
"Bin",
""
],
[
"Xu",
"Zhen-Ming",
""
],
[
"Yang",
"Wen-Li",
""
]
] | The connection between the shadow radius and the Ruppeiner geometry of a charged static spherically symmetric black hole is investigated. The normalized curvature scalar is adopted, and its close relation to the Van der Waals-like and Hawking-Page phase transition of Reissner-Nordstr\"{o}m AdS black hole is studied. The results show that the shadow radius is a useful tool to reveal the correct information of the phase structure and the underlying microstructure of the black hole, which opens a new window to investigate the strong gravity system from the observational point of view. |
2009.05193 | Yun Soo Myung | Yun Soo Myung, De-Cheng Zou | Scalarized charged black holes in the Einstein-Maxwell-Scalar theory
with two U(1) fields | 20 pages, 10 figures | null | 10.1016/j.physletb.2020.135905 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate scalarized charged black holes in the Einstein-Maxwell-Scalar
theory with two U(1) fields inspired by the $N=4$ supergravity. From the onset
of the spontaneous scalarization (tachyonic instability of
Reissner-Nordstr\"{o}m black hole), these black holes are classified by the
number of $n=0,1,2,\cdots$, where $n=0$ is called the fundamental black hole
and $n=1,2,\cdots$ denote the $n$-excited black holes. Adopting radial
perturbations, we show that the $n=0$ black hole is stable against the
$s(l=0)$-mode scalar perturbation, whereas the $n=1,2$ excited black holes are
unstable. This implies that the $n=0$ black hole is considered as an endpoint
of the Reissner-Nordstr\"{o}m black hole.
| [
{
"created": "Fri, 11 Sep 2020 01:29:22 GMT",
"version": "v1"
}
] | 2020-11-04 | [
[
"Myung",
"Yun Soo",
""
],
[
"Zou",
"De-Cheng",
""
]
] | We investigate scalarized charged black holes in the Einstein-Maxwell-Scalar theory with two U(1) fields inspired by the $N=4$ supergravity. From the onset of the spontaneous scalarization (tachyonic instability of Reissner-Nordstr\"{o}m black hole), these black holes are classified by the number of $n=0,1,2,\cdots$, where $n=0$ is called the fundamental black hole and $n=1,2,\cdots$ denote the $n$-excited black holes. Adopting radial perturbations, we show that the $n=0$ black hole is stable against the $s(l=0)$-mode scalar perturbation, whereas the $n=1,2$ excited black holes are unstable. This implies that the $n=0$ black hole is considered as an endpoint of the Reissner-Nordstr\"{o}m black hole. |
1111.3536 | Stoytcho Yazadjiev | Stoytcho Yazadjiev | Relativistic models of magnetars: Nonperturbative analytical approach | 10 pages, LaTex | null | 10.1103/PhysRevD.85.044030 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we focus on building simple nonperturbative analytical
relativistic models of magnetars. With this purpose in mind we first develop a
method for generating exact interior solutions to the static and axisymmetric
Einstein-Maxwell-hydrodynamic equations with anisotropic perfect fluid and with
pure poloidal magnetic field. Then using an explicit exact solution we present
a simple magnetar model and calculate some physically interesting quantities as
the surface elipticity and the total energy of the magnetized star.
| [
{
"created": "Tue, 15 Nov 2011 14:37:15 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Yazadjiev",
"Stoytcho",
""
]
] | In the present paper we focus on building simple nonperturbative analytical relativistic models of magnetars. With this purpose in mind we first develop a method for generating exact interior solutions to the static and axisymmetric Einstein-Maxwell-hydrodynamic equations with anisotropic perfect fluid and with pure poloidal magnetic field. Then using an explicit exact solution we present a simple magnetar model and calculate some physically interesting quantities as the surface elipticity and the total energy of the magnetized star. |
0803.1485 | Daniel Grumiller | D. Grumiller, R. Mann and R. McNees | Dirichlet boundary value problem for Chern-Simons modified gravity | 4 pages, revtex4, v2: added Refs., made one statement stronger, added
footnote and added paragraph on single field inflation | Phys.Rev.D78:081502,2008 | 10.1103/PhysRevD.78.081502 | MIT-CTP 3933 | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Chern-Simons modified gravity comprises the Einstein-Hilbert action and a
higher-derivative interaction containing the Chern-Pontryagin density. We
derive the analog of the Gibbons-Hawking-York boundary term required to render
the Dirichlet boundary value problem well-defined. It turns out to be a
boundary Chern-Simons action for the extrinsic curvature. We address
applications to black hole thermodynamics.
| [
{
"created": "Mon, 10 Mar 2008 20:01:01 GMT",
"version": "v1"
},
{
"created": "Tue, 20 May 2008 21:29:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Grumiller",
"D.",
""
],
[
"Mann",
"R.",
""
],
[
"McNees",
"R.",
""
]
] | Chern-Simons modified gravity comprises the Einstein-Hilbert action and a higher-derivative interaction containing the Chern-Pontryagin density. We derive the analog of the Gibbons-Hawking-York boundary term required to render the Dirichlet boundary value problem well-defined. It turns out to be a boundary Chern-Simons action for the extrinsic curvature. We address applications to black hole thermodynamics. |
2012.00599 | David Garfinkle | David Garfinkle | The electric field of a charge in the vicinity of a higher dimensional
black hole | null | Phys. Rev. D 103, 024056 (2021) | 10.1103/PhysRevD.103.024056 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find the electric field of a point charge in the presence of a higher
dimensional black hole. As the charge is lowered to the horizon, all higher
multipole moments go to zero, and only the Coulomb field remains.
| [
{
"created": "Tue, 1 Dec 2020 16:08:05 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Garfinkle",
"David",
""
]
] | We find the electric field of a point charge in the presence of a higher dimensional black hole. As the charge is lowered to the horizon, all higher multipole moments go to zero, and only the Coulomb field remains. |
1711.04137 | Soumya Jana | Soumya Jana, Girish Kumar Chakravarty, Subhendra Mohanty (PRL
Ahmedabad, India) | Constraints on Born-Infeld gravity from the speed of gravitational waves
after GW170817 and GRB 170817A | 5 pages. Published version | Phys. Rev. D 97, 084011 (2018) | 10.1103/PhysRevD.97.084011 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observations of gravitational waves from the binary neutron star merger
event GW170817 and the subsequent observation of its electromagnetic
counterparts from the gamma-ray burst GRB 170817A provide us a significant
opportunity to study theories of gravity beyond general relativity. An
important outcome of these observations is that they constrain the difference
between the speed of gravity and the speed of light to less than $10^{-15}c$.
Also, the time delay between the arrivals of gravitational waves at different
detectors constrains the speed of gravity at the Earth to be in the range
$0.55c < v_{gw} < 1.42c$. We use these results to constrain a widely studied
modified theory of gravity: Eddington-inspired Born-Infeld (EiBI) gravity. We
show that, in EiBI theory, the speed of gravitational waves in matter deviates
from $c$. From the time delay in arrival of gravitational wave signals at
Earth-based detectors, we obtain the bound on the theory parameter $\kappa$ as
$\vert\kappa\vert \lesssim 10^{21}\, m^2$. Similarly, from the time delay
between the signals of GW170817 and GRB 170817A, in a background
Friedmann-Robertson-Walker universe, we obtain $\vert \kappa \vert \lesssim
10^{37}\, m^2$. Although the bounds on $\kappa$ are weak compared to other
earlier bounds from the study of neutron stars, stellar evolution, primordial
nucleosynthesis, etc., our bounds are from the direct observations and thus
worth noting.
| [
{
"created": "Sat, 11 Nov 2017 13:59:39 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Apr 2018 13:33:43 GMT",
"version": "v2"
}
] | 2018-04-11 | [
[
"Jana",
"Soumya",
"",
"PRL\n Ahmedabad, India"
],
[
"Chakravarty",
"Girish Kumar",
"",
"PRL\n Ahmedabad, India"
],
[
"Mohanty",
"Subhendra",
"",
"PRL\n Ahmedabad, India"
]
] | The observations of gravitational waves from the binary neutron star merger event GW170817 and the subsequent observation of its electromagnetic counterparts from the gamma-ray burst GRB 170817A provide us a significant opportunity to study theories of gravity beyond general relativity. An important outcome of these observations is that they constrain the difference between the speed of gravity and the speed of light to less than $10^{-15}c$. Also, the time delay between the arrivals of gravitational waves at different detectors constrains the speed of gravity at the Earth to be in the range $0.55c < v_{gw} < 1.42c$. We use these results to constrain a widely studied modified theory of gravity: Eddington-inspired Born-Infeld (EiBI) gravity. We show that, in EiBI theory, the speed of gravitational waves in matter deviates from $c$. From the time delay in arrival of gravitational wave signals at Earth-based detectors, we obtain the bound on the theory parameter $\kappa$ as $\vert\kappa\vert \lesssim 10^{21}\, m^2$. Similarly, from the time delay between the signals of GW170817 and GRB 170817A, in a background Friedmann-Robertson-Walker universe, we obtain $\vert \kappa \vert \lesssim 10^{37}\, m^2$. Although the bounds on $\kappa$ are weak compared to other earlier bounds from the study of neutron stars, stellar evolution, primordial nucleosynthesis, etc., our bounds are from the direct observations and thus worth noting. |
gr-qc/0504112 | Andrzej Krolak | Jeffrey A. Edlund, Massimo Tinto, Andrzej Krolak, and Gijs Nelemans | The White Dwarf -- White Dwarf galactic background in the LISA data | 36 pages, 15 figures | Phys.Rev.D71:122003,2005 | 10.1103/PhysRevD.71.122003 | null | gr-qc | null | LISA (Laser Interferometer Space Antenna) is a proposed space mission, which
will use coherent laser beams exchanged between three remote spacecraft to
detect and study low-frequency cosmic gravitational radiation. In the low-part
of its frequency band, the LISA strain sensitivity will be dominated by the
incoherent superposition of hundreds of millions of gravitational wave signals
radiated by inspiraling white-dwarf binaries present in our own galaxy. In
order to estimate the magnitude of the LISA response to this background, we
have simulated a synthesized population that recently appeared in the
literature. We find the amplitude of the galactic white-dwarf binary background
in the LISA data to be modulated in time, reaching a minimum equal to about
twice that of the LISA noise for a period of about two months around the time
when the Sun-LISA direction is roughly oriented towards the Autumn equinox.
Since the galactic white-dwarfs background will be observed by LISA not as a
stationary but rather as a cyclostationary random process with a period of one
year, we summarize the theory of cyclostationary random processes, present the
corresponding generalized spectral method needed to characterize such process,
and make a comparison between our analytic results and those obtained by
applying our method to the simulated data. We find that, by measuring the
generalized spectral components of the white-dwarf background, LISA will be
able to infer properties of the distribution of the white-dwarfs binary systems
present in our Galaxy.
| [
{
"created": "Fri, 22 Apr 2005 17:44:29 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Edlund",
"Jeffrey A.",
""
],
[
"Tinto",
"Massimo",
""
],
[
"Krolak",
"Andrzej",
""
],
[
"Nelemans",
"Gijs",
""
]
] | LISA (Laser Interferometer Space Antenna) is a proposed space mission, which will use coherent laser beams exchanged between three remote spacecraft to detect and study low-frequency cosmic gravitational radiation. In the low-part of its frequency band, the LISA strain sensitivity will be dominated by the incoherent superposition of hundreds of millions of gravitational wave signals radiated by inspiraling white-dwarf binaries present in our own galaxy. In order to estimate the magnitude of the LISA response to this background, we have simulated a synthesized population that recently appeared in the literature. We find the amplitude of the galactic white-dwarf binary background in the LISA data to be modulated in time, reaching a minimum equal to about twice that of the LISA noise for a period of about two months around the time when the Sun-LISA direction is roughly oriented towards the Autumn equinox. Since the galactic white-dwarfs background will be observed by LISA not as a stationary but rather as a cyclostationary random process with a period of one year, we summarize the theory of cyclostationary random processes, present the corresponding generalized spectral method needed to characterize such process, and make a comparison between our analytic results and those obtained by applying our method to the simulated data. We find that, by measuring the generalized spectral components of the white-dwarf background, LISA will be able to infer properties of the distribution of the white-dwarfs binary systems present in our Galaxy. |
1604.06893 | Pradip Mukherjee | Rabin Banerjee and Pradip Mukherjee | Torsional Newton-Cartan geometry from Galilean gauge theory | 21 pages, latex, journal version | Class. Quantum Grav. 33 225013 2016 | 10.1088/0264-9381/33/22/225013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the recently advanced Galilean gauge theory (GGT) we give a
comprehensive construction of torsional Newton Cartan geometry. The coupling of
a Galilean symmetric model with background NC geometry following GGT is
illustrated by a free nonrelativistic scalar field theory. The issue of spatial
diffeomorphisn \cite{SW, BMM3} is focussed from a new angle. The expression of
the torsionful connection is worked out which is in complete parallel with the
relativistic theory. Also smooth transition of the connection to its well known
torsionless expression is demonstrated. A complete (implicit) expression of the
torsion tensor for the Newton Cartan spacetime is provided where the first
order variables occur in a suggestive way. The well known result for the
temporal part of torsion is reproduced from our expression.
| [
{
"created": "Sat, 23 Apr 2016 11:01:01 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jul 2016 18:22:24 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Nov 2016 07:24:31 GMT",
"version": "v3"
}
] | 2016-11-03 | [
[
"Banerjee",
"Rabin",
""
],
[
"Mukherjee",
"Pradip",
""
]
] | Using the recently advanced Galilean gauge theory (GGT) we give a comprehensive construction of torsional Newton Cartan geometry. The coupling of a Galilean symmetric model with background NC geometry following GGT is illustrated by a free nonrelativistic scalar field theory. The issue of spatial diffeomorphisn \cite{SW, BMM3} is focussed from a new angle. The expression of the torsionful connection is worked out which is in complete parallel with the relativistic theory. Also smooth transition of the connection to its well known torsionless expression is demonstrated. A complete (implicit) expression of the torsion tensor for the Newton Cartan spacetime is provided where the first order variables occur in a suggestive way. The well known result for the temporal part of torsion is reproduced from our expression. |
gr-qc/9812018 | Yogesh Joglekar | Tulsi Dass, Yogesh N. Joglekar (Indian Institute of Technology,
Kanpur, India) | Symmetries and conservation laws in histories-based generalized quantum
mechanics | 31 pages. Several typos corrected. A combined version of this paper
and gr-qc/9905028 (available at gr-qc/0001006) will be published in Annals of
Physics | null | null | null | gr-qc quant-ph | null | Symmetries are defined in histories-based generalized quantum mechanics
paying special attention to the class of history theories admitting
quasitemporal structure (a generalization of the concept of `temporal
sequences' of `events' using partial semigroups) and logic structure for
`single time histories'. Symmetries are classified into orthochronous (those
preserving the `temporal order' of `events') and non-orthochronous. A
straightforward criterion for physical equivalence of histories is formulated
in terms of orthochronous symmetries; this criterion covers various notions of
physical equivalence considered by Gell-Mann and Hartle as special cases. In
familiar situations, a reciprocal relationship between traditional symmetries
(Wigner symmetries in quantum mechanics and Borel-measurable transformations of
phase space in classical mechanics) and symmetries defined in this work is
established. In a restricted class of theories, a definition of conservation
law is given in the history language which agrees with the standard ones in
familiar situations; in a smaller subclass of theories, a Noether type theorem
(implying a connection between continuous symmetries of dynamics and
conservation laws) is proved.
| [
{
"created": "Sat, 5 Dec 1998 00:44:40 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Dec 1998 01:10:46 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Dec 1998 00:38:14 GMT",
"version": "v3"
},
{
"created": "Sun, 17 Sep 2000 20:39:03 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Dass",
"Tulsi",
"",
"Indian Institute of Technology,\n Kanpur, India"
],
[
"Joglekar",
"Yogesh N.",
"",
"Indian Institute of Technology,\n Kanpur, India"
]
] | Symmetries are defined in histories-based generalized quantum mechanics paying special attention to the class of history theories admitting quasitemporal structure (a generalization of the concept of `temporal sequences' of `events' using partial semigroups) and logic structure for `single time histories'. Symmetries are classified into orthochronous (those preserving the `temporal order' of `events') and non-orthochronous. A straightforward criterion for physical equivalence of histories is formulated in terms of orthochronous symmetries; this criterion covers various notions of physical equivalence considered by Gell-Mann and Hartle as special cases. In familiar situations, a reciprocal relationship between traditional symmetries (Wigner symmetries in quantum mechanics and Borel-measurable transformations of phase space in classical mechanics) and symmetries defined in this work is established. In a restricted class of theories, a definition of conservation law is given in the history language which agrees with the standard ones in familiar situations; in a smaller subclass of theories, a Noether type theorem (implying a connection between continuous symmetries of dynamics and conservation laws) is proved. |
1011.0875 | Mubasher Jamil | M. R. Setare and Mubasher Jamil | Correspondence between entropy-corrected holographic and Gauss-Bonnet
dark energy models | 10 pages, accepted by Europhysics Letters for publication | Europhys.Lett.92:49003,2010 | 10.1209/0295-5075/92/49003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we investigate the cosmological implications of the
entropy-corrected holographic dark energy (ECHDE) density in the Gauss-Bonnet
framework. This is motivated from the loop quantum gravity corrections to the
entropy-area law. Assuming the two cosmological scenarios are valid
simultaneously, we show that there is a correspondence between the ECHDE
scenario in flat universe and the phantom dark energy model in the framework of
Gauss-Bonnet theory with a potential. This correspondence leads consistently to
an accelerating universe.
| [
{
"created": "Wed, 3 Nov 2010 13:32:11 GMT",
"version": "v1"
}
] | 2011-01-28 | [
[
"Setare",
"M. R.",
""
],
[
"Jamil",
"Mubasher",
""
]
] | In the present work we investigate the cosmological implications of the entropy-corrected holographic dark energy (ECHDE) density in the Gauss-Bonnet framework. This is motivated from the loop quantum gravity corrections to the entropy-area law. Assuming the two cosmological scenarios are valid simultaneously, we show that there is a correspondence between the ECHDE scenario in flat universe and the phantom dark energy model in the framework of Gauss-Bonnet theory with a potential. This correspondence leads consistently to an accelerating universe. |
2107.14666 | Andr\'e Gro{\ss}ardt | Andr\'e Gro{\ss}ardt | Comment on "Do Gedankenexperiments compel quantization of gravity" | Comment on arXiv:2107.07514 | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | There is no conclusive theoretical argument that would require the
quantization of the gravitational field. A paradox presented by Mari et al.
[Sci. Rep. 6, 22777 (2016)] and its resolution by Belenchia et al. [Phys. Rev.
D 98, 126009 (2018)] did not change anything about this assertion. Despite
being interesting in other respects, efforts of a recent work by Ryding,
Aurell, and Pikovski [arXiv:2107.07514] to further establish the
inconclusiveness of the question of necessity of quantization are futile.
| [
{
"created": "Fri, 30 Jul 2021 14:36:22 GMT",
"version": "v1"
}
] | 2021-08-02 | [
[
"Großardt",
"André",
""
]
] | There is no conclusive theoretical argument that would require the quantization of the gravitational field. A paradox presented by Mari et al. [Sci. Rep. 6, 22777 (2016)] and its resolution by Belenchia et al. [Phys. Rev. D 98, 126009 (2018)] did not change anything about this assertion. Despite being interesting in other respects, efforts of a recent work by Ryding, Aurell, and Pikovski [arXiv:2107.07514] to further establish the inconclusiveness of the question of necessity of quantization are futile. |
gr-qc/9502032 | Olga Buryak | O. E. Buryak | STOCHASTIC DYNAMICS OF LARGE-SCALE INFLATION IN DE~SITTER SPACE | 21 pages RevTex preprint style | Phys.Rev. D53 (1996) 1763-1775 | 10.1103/PhysRevD.53.1763 | NCL95-TP1 | gr-qc | null | In this paper we derive exact quantum Langevin equations for stochastic
dynamics of large-scale inflation in de~Sitter space. These quantum Langevin
equations are the equivalent of the Wigner equation and are described by a
system of stochastic differential equations. We present a formula for the
calculation of the expectation value of a quantum operator whose Weyl symbol is
a function of the large-scale inflation scalar field and its time derivative.
The unique solution is obtained for the Cauchy problem for the Wigner equation
for large-scale inflation. The stationary solution for the Wigner equation is
found for an arbitrary potential. It is shown that the large-scale inflation
scalar field in de Sitter space behaves as a quantum one-dimensional
dissipative system, which supports the earlier results. But the analogy with a
one-dimensional model of the quantum linearly damped anharmonic oscillator is
not complete: the difference arises from the new time dependent commutation
relation for the large-scale field and its time derivative. It is found that,
for the large-scale inflation scalar field the large time asymptotics is equal
to the `classical limit'. For the large time limit the quantum Langevin
equations are just the classical stochastic Langevin equations (only the
stationary state is defined by the quantum field theory).
| [
{
"created": "Thu, 16 Feb 1995 12:09:06 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Buryak",
"O. E.",
""
]
] | In this paper we derive exact quantum Langevin equations for stochastic dynamics of large-scale inflation in de~Sitter space. These quantum Langevin equations are the equivalent of the Wigner equation and are described by a system of stochastic differential equations. We present a formula for the calculation of the expectation value of a quantum operator whose Weyl symbol is a function of the large-scale inflation scalar field and its time derivative. The unique solution is obtained for the Cauchy problem for the Wigner equation for large-scale inflation. The stationary solution for the Wigner equation is found for an arbitrary potential. It is shown that the large-scale inflation scalar field in de Sitter space behaves as a quantum one-dimensional dissipative system, which supports the earlier results. But the analogy with a one-dimensional model of the quantum linearly damped anharmonic oscillator is not complete: the difference arises from the new time dependent commutation relation for the large-scale field and its time derivative. It is found that, for the large-scale inflation scalar field the large time asymptotics is equal to the `classical limit'. For the large time limit the quantum Langevin equations are just the classical stochastic Langevin equations (only the stationary state is defined by the quantum field theory). |
1407.8143 | Giulia Gubitosi | Giovanni Amelino-Camelia, Leonardo Barcaroli, Giulia Gubitosi, Stefano
Liberati, Niccol\'o Loret | Realization of DSR-relativistic symmetries in Finsler geometries | null | Phys. Rev. D 90, 125030 (2014) | 10.1103/PhysRevD.90.125030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finsler geometry is a well known generalization of Riemannian geometry which
allows to account for a possibly non trivial structure of the space of
configurations of relativistic particles. We here establish a link between
Finsler geometry and the sort of models with curved momentum space and
DSR-relativistic symmetries which have been recently of interest in the
quantum-gravity literature. We use as case study the much-studied scenario
which is inspired by the $\kappa$-Poincar\'e quantum group, and show that the
relevant deformation of relativistic symmetries can be implemented within a
Finsler geometry.
| [
{
"created": "Wed, 30 Jul 2014 17:56:38 GMT",
"version": "v1"
}
] | 2015-01-07 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Barcaroli",
"Leonardo",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Loret",
"Niccoló",
""
]
] | Finsler geometry is a well known generalization of Riemannian geometry which allows to account for a possibly non trivial structure of the space of configurations of relativistic particles. We here establish a link between Finsler geometry and the sort of models with curved momentum space and DSR-relativistic symmetries which have been recently of interest in the quantum-gravity literature. We use as case study the much-studied scenario which is inspired by the $\kappa$-Poincar\'e quantum group, and show that the relevant deformation of relativistic symmetries can be implemented within a Finsler geometry. |
1907.02924 | Marco Crisostomi | Christos Charmousis, Marco Crisostomi, David Langlois, Karim Noui | Perturbations of a rotating black hole in DHOST theories | 6 pages | null | 10.1088/1361-6382/ab4fb1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear perturbations of a rotating black hole solution that has been
recently discovered in degenerate higher-order scalar-tensor (DHOST) theories.
We find a parametrization which permits the explicit resolution of the scalar
perturbation while the tensor perturbation is obtained as a Teukolsky equation
supplemented by an effective source term. The effective source term is related
to the black hole hair and can be computed exactly for any value of the black
hole spin. We discuss how the perturbations of the geometry and thus the
emitted gravitational waves could be modified in comparison with general
relativity.
| [
{
"created": "Fri, 5 Jul 2019 16:48:02 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Charmousis",
"Christos",
""
],
[
"Crisostomi",
"Marco",
""
],
[
"Langlois",
"David",
""
],
[
"Noui",
"Karim",
""
]
] | We study linear perturbations of a rotating black hole solution that has been recently discovered in degenerate higher-order scalar-tensor (DHOST) theories. We find a parametrization which permits the explicit resolution of the scalar perturbation while the tensor perturbation is obtained as a Teukolsky equation supplemented by an effective source term. The effective source term is related to the black hole hair and can be computed exactly for any value of the black hole spin. We discuss how the perturbations of the geometry and thus the emitted gravitational waves could be modified in comparison with general relativity. |
1801.01912 | Ali A. Asgari | Ali A. Asgari, Amir H. Abbassi, Jafar Khodagholizadeh | Curvature and topology dependency of the cosmological spectra | 9 pages,12 figures | Results Phys 12, 2225 (2019) | 10.1016/j.rinp.2019.02.039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we investigate dependency of the adiabatic and entropy
spectral indices of the cosmological perturbations on the geometry and topology
of the background universe. Our discussion includes the post-inflationary
universe i.e. radiation-dust mixture era. For this purpose, we first extract an
explicit equation describing evolution of the comoving curvature perturbation
in the FLRW universe with arbitrary spatial sectional curvature. We may percept
when $K\neq 0$, curvature scale would be as significant as the perturbations
scales to recognize the behavior of the spectral indices. We also focus on the
entropy perturbation in order to extract behavior of the isocurvature spectral
index in terms of the curvature index and time. Our analysis shows that spectra
of curvature and entropy perturbations in sub-horizon scales could be function
of topology. Moreover, an accurate analysis makes clear that time-average of
isocurvature index in case $K=0$ is about zero,so that imprint of entropy
perturbation in time duration may be negligible. We also consider evolution of
the cosmological indices for super-curvature modes in the case $K=-1$. In the
most results dependency to curvature, initial conditions and scale modes are
thoroughly vivid.
| [
{
"created": "Fri, 5 Jan 2018 20:39:47 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Mar 2019 22:57:41 GMT",
"version": "v2"
}
] | 2019-03-11 | [
[
"Asgari",
"Ali A.",
""
],
[
"Abbassi",
"Amir H.",
""
],
[
"Khodagholizadeh",
"Jafar",
""
]
] | In this article we investigate dependency of the adiabatic and entropy spectral indices of the cosmological perturbations on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e. radiation-dust mixture era. For this purpose, we first extract an explicit equation describing evolution of the comoving curvature perturbation in the FLRW universe with arbitrary spatial sectional curvature. We may percept when $K\neq 0$, curvature scale would be as significant as the perturbations scales to recognize the behavior of the spectral indices. We also focus on the entropy perturbation in order to extract behavior of the isocurvature spectral index in terms of the curvature index and time. Our analysis shows that spectra of curvature and entropy perturbations in sub-horizon scales could be function of topology. Moreover, an accurate analysis makes clear that time-average of isocurvature index in case $K=0$ is about zero,so that imprint of entropy perturbation in time duration may be negligible. We also consider evolution of the cosmological indices for super-curvature modes in the case $K=-1$. In the most results dependency to curvature, initial conditions and scale modes are thoroughly vivid. |
gr-qc/0308047 | Eirini Messaritaki | Eirini Messaritaki (University of Florida) | Radiation Reaction on Moving Particles in General Relativity | Doctoral Dissertation, 136 pages, 5 figures | null | null | null | gr-qc | null | A particle in the vicinity of a Schwarzschild black hole is known to trace a
geodesic of the Schwarzschild background, to a first approximation. If the
interaction of the particle with its own field (scalar, electromagnetic or
gravitational) is taken into account, the path is no longer a background
geodesic and the self-force that the particle experiences needs to be taken
into consideration.
In this dissertation, a recently proposed method for the calculation of the
self-force is implemented. According to this method the self-force comes from
the interaction of the particle with the Regular-Remainder scalar field,
electromagnetic potential or metric perturbation. That Regular-Remainder is
obtained by subtracting the Singular part (which exerts no force) from the
retarded scalar field, electromagnetic potential of metric perturbation
generated by the moving particle. First, the Singular scalar fields,
electromagnetic potentials and metric perturbations are calculated for
different sources moving in a Schwarzschild background. For that, the
Thorne-Hartle-Zhang coordinates in the vicinity of the moving source are used.
Then a mode-sum regularization method initially proposed for the direct scalar
field is followed, and the regularization parameters for the singular part of
the scalar field and for the first radial derivative of the singular part of
the self-force are calculated. Also, the numerical calculation of the retarded
scalar field for a particle moving on a circular geodesic in a Schwarzschild
spacetime is presented. Finally, the self-force for a scalar particle moving on
a circular Schwarzschild orbit is calculated and some results about the effects
of the self-force on the orbital frequency of the circular orbit are presented.
| [
{
"created": "Thu, 14 Aug 2003 18:19:48 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Messaritaki",
"Eirini",
"",
"University of Florida"
]
] | A particle in the vicinity of a Schwarzschild black hole is known to trace a geodesic of the Schwarzschild background, to a first approximation. If the interaction of the particle with its own field (scalar, electromagnetic or gravitational) is taken into account, the path is no longer a background geodesic and the self-force that the particle experiences needs to be taken into consideration. In this dissertation, a recently proposed method for the calculation of the self-force is implemented. According to this method the self-force comes from the interaction of the particle with the Regular-Remainder scalar field, electromagnetic potential or metric perturbation. That Regular-Remainder is obtained by subtracting the Singular part (which exerts no force) from the retarded scalar field, electromagnetic potential of metric perturbation generated by the moving particle. First, the Singular scalar fields, electromagnetic potentials and metric perturbations are calculated for different sources moving in a Schwarzschild background. For that, the Thorne-Hartle-Zhang coordinates in the vicinity of the moving source are used. Then a mode-sum regularization method initially proposed for the direct scalar field is followed, and the regularization parameters for the singular part of the scalar field and for the first radial derivative of the singular part of the self-force are calculated. Also, the numerical calculation of the retarded scalar field for a particle moving on a circular geodesic in a Schwarzschild spacetime is presented. Finally, the self-force for a scalar particle moving on a circular Schwarzschild orbit is calculated and some results about the effects of the self-force on the orbital frequency of the circular orbit are presented. |
2206.06750 | Dipanjan Dey | Vishva Patel, Divya Tahelyani, Ashok B. Joshi, Dipanjan Dey, Pankaj S.
Joshi | Light trajectory and shadow shape in the rotating naked singularity | 12 pages, 4 figures | null | 10.1140/epjc/s10052-022-10638-w | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the light trajectories and shadow properties in
the rotating version of null naked singularity (NNS) spacetime which is derived
using the Newman- Janis algorithm without complexification method. We discuss
some of the geometrical properties and causal structure of Rotating Naked
Singularity (RNS) spacetime. The gravitational lensing in a rotating naked
singularity is analyzed, and the results are compared to those of a Kerr black
hole. In the case of a Kerr black hole, the photon sphere exists for both
prograde and retrograde photon orbits, whereas for RNS, the photon sphere
exists only for retrograde photon orbits. As a result, the naked singularity
projects an arc-shaped shadow that differs from the contour-shaped shadow cast
by a Kerr black hole.
| [
{
"created": "Tue, 14 Jun 2022 10:50:16 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Patel",
"Vishva",
""
],
[
"Tahelyani",
"Divya",
""
],
[
"Joshi",
"Ashok B.",
""
],
[
"Dey",
"Dipanjan",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | In this paper, we investigate the light trajectories and shadow properties in the rotating version of null naked singularity (NNS) spacetime which is derived using the Newman- Janis algorithm without complexification method. We discuss some of the geometrical properties and causal structure of Rotating Naked Singularity (RNS) spacetime. The gravitational lensing in a rotating naked singularity is analyzed, and the results are compared to those of a Kerr black hole. In the case of a Kerr black hole, the photon sphere exists for both prograde and retrograde photon orbits, whereas for RNS, the photon sphere exists only for retrograde photon orbits. As a result, the naked singularity projects an arc-shaped shadow that differs from the contour-shaped shadow cast by a Kerr black hole. |
1305.5191 | Jan Holland | Jan Holland and Stefan Hollands | A small cosmological constant due to non-perturbative quantum effects | 11 pages | Class. Quantum Grav. 31 (2014) 125006 | 10.1088/0264-9381/31/12/125006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that the expectation value of the stress energy tensor of the
Standard Model should be given by $< T_{\mu \nu} > = \rho_\vac \eta_{\mu\nu}$,
with a vacuum energy $\rho_\vac$ that differs from the usual "dimensional
analysis" result by an exponentially small factor associated with
non-perturbative effects. We substantiate our proposal by a rigorous analysis
of a toy model, namely the 2-dimensional Gross-Neveu model. In particular, we
address, within this model, the key question of the renormalization ambiguities
affecting the calculation. The stress energy operator is constructed concretely
via the operator-product-expansion. The non-perturbative factor in the vacuum
energy is seen as a consequence of the facts that a) the OPE-coefficients have
an analytic dependence on $g$, b) the vacuum correlations have a non-analytic
(=non-perturbative) dependence on $g$, which we propose to be a generic feature
of QFT. Extrapolating our result from the Gross-Neveu model to the Standard
Model, one would expect to find $\rho_\vac ~ \Lambda^4 \e^{-O(1)/g^2}$, where
$\Lambda$ is an energy scale such as $\Lambda = M_{H}$, and $g$ is a gauge
coupling such as $g^2/4\pi = \alpha_{EW}$. The exponentially small factor due
to non-perturbative effects could explain the "unnatural" smallness of this
quantity.
| [
{
"created": "Wed, 22 May 2013 16:49:02 GMT",
"version": "v1"
}
] | 2014-06-02 | [
[
"Holland",
"Jan",
""
],
[
"Hollands",
"Stefan",
""
]
] | We propose that the expectation value of the stress energy tensor of the Standard Model should be given by $< T_{\mu \nu} > = \rho_\vac \eta_{\mu\nu}$, with a vacuum energy $\rho_\vac$ that differs from the usual "dimensional analysis" result by an exponentially small factor associated with non-perturbative effects. We substantiate our proposal by a rigorous analysis of a toy model, namely the 2-dimensional Gross-Neveu model. In particular, we address, within this model, the key question of the renormalization ambiguities affecting the calculation. The stress energy operator is constructed concretely via the operator-product-expansion. The non-perturbative factor in the vacuum energy is seen as a consequence of the facts that a) the OPE-coefficients have an analytic dependence on $g$, b) the vacuum correlations have a non-analytic (=non-perturbative) dependence on $g$, which we propose to be a generic feature of QFT. Extrapolating our result from the Gross-Neveu model to the Standard Model, one would expect to find $\rho_\vac ~ \Lambda^4 \e^{-O(1)/g^2}$, where $\Lambda$ is an energy scale such as $\Lambda = M_{H}$, and $g$ is a gauge coupling such as $g^2/4\pi = \alpha_{EW}$. The exponentially small factor due to non-perturbative effects could explain the "unnatural" smallness of this quantity. |
gr-qc/0512078 | Stephen Fairhurst | LIGO Scientific Collaboration, TAMA Collaboration | Joint LIGO and TAMA300 Search for Gravitational Waves from Inspiralling
Neutron Star Binaries | 9 pages, 5 figures. Updated with published version | Phys.Rev.D73:102002,2006 | 10.1103/PhysRevD.73.102002 | LIGO-P050017-01-Z | gr-qc | null | We search for coincident gravitational wave signals from inspiralling neutron
star binaries using LIGO and TAMA300 data taken during early 2003. Using a
simple trigger exchange method, we perform an inter-collaboration coincidence
search during times when TAMA300 and only one of the LIGO sites were
operational. We find no evidence of any gravitational wave signals. We place an
observational upper limit on the rate of binary neutron star coalescence with
component masses between 1 and 3 M_sun of 49 per year per Milky Way equivalent
galaxy at a 90% confidence level. The methods developed during this search will
find application in future network inspiral analyses.
| [
{
"created": "Tue, 13 Dec 2005 16:26:56 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Oct 2006 18:44:09 GMT",
"version": "v2"
}
] | 2012-08-27 | [
[
"LIGO Scientific Collaboration",
"",
""
],
[
"TAMA Collaboration",
"",
""
]
] | We search for coincident gravitational wave signals from inspiralling neutron star binaries using LIGO and TAMA300 data taken during early 2003. Using a simple trigger exchange method, we perform an inter-collaboration coincidence search during times when TAMA300 and only one of the LIGO sites were operational. We find no evidence of any gravitational wave signals. We place an observational upper limit on the rate of binary neutron star coalescence with component masses between 1 and 3 M_sun of 49 per year per Milky Way equivalent galaxy at a 90% confidence level. The methods developed during this search will find application in future network inspiral analyses. |
gr-qc/9503008 | Paulo Rodrigues Lima Vargas Moniz | O. Bertolami (INFN - Sezione Torino) and P.V. Moniz (University of
Cambridge, DAMTP) | Decoherence Due to Massive Vector Fields with Global Symmetries | 5 pages, Talk at the 1st Mexican School in Gravitation and
mathematical physics, Guanajuato, Mexico, December 12-16 1994 | null | null | DAMTP R-94/22c | gr-qc | null | Retrieval of classical behaviour in quantum cosmology is usually discussed in
the framework of minisuperspace models in the presence of scalar fields
together with the inhomogeneous modes of gravitational or scalar fields. In
this work we propose alternatively a model where the scalar field is replaced
by a massive vector field with global U(1) or SO(3) internal symmetries.
| [
{
"created": "Mon, 6 Mar 1995 14:03:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bertolami",
"O.",
"",
"INFN - Sezione Torino"
],
[
"Moniz",
"P. V.",
"",
"University of\n Cambridge, DAMTP"
]
] | Retrieval of classical behaviour in quantum cosmology is usually discussed in the framework of minisuperspace models in the presence of scalar fields together with the inhomogeneous modes of gravitational or scalar fields. In this work we propose alternatively a model where the scalar field is replaced by a massive vector field with global U(1) or SO(3) internal symmetries. |
1803.07093 | Shahar Hod | Shahar Hod | Stationary bound-state scalar configurations supported by
rapidly-spinning exotic compact objects | 11 pages. arXiv admin note: text overlap with arXiv:1704.05856 | Physics Letters B 770, 186 (2017) | 10.1016/j.physletb.2017.04.065 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some quantum-gravity theories suggest that the absorbing horizon of a
classical black hole should be replaced by a reflective surface which is
located a microscopic distance above the would-be classical horizon. Instead of
an absorbing black hole, the resulting horizonless spacetime describes a
reflective exotic compact object. Motivated by this intriguing prediction, in
the present paper we explore the physical properties of exotic compact objects
which are linearly coupled to stationary bound-state massive scalar field
configurations. In particular, solving the Klein-Gordon wave equation for a
stationary scalar field of proper mass $\mu$ and spheroidal harmonic indices
$(l,m)$ in the background of a rapidly-rotating exotic compact object of mass
$M$ and angular momentum $J=Ma$, we derive a compact analytical formula for the
{\it discrete} radii $\{r_{\text{c}}(\mu,l,m,M,a;n)\}$ of the exotic compact
objects which can support the stationary bound-state massive scalar field
configurations. We confirm our analytical results by direct numerical
computations.
| [
{
"created": "Mon, 19 Mar 2018 18:01:00 GMT",
"version": "v1"
}
] | 2018-03-28 | [
[
"Hod",
"Shahar",
""
]
] | Some quantum-gravity theories suggest that the absorbing horizon of a classical black hole should be replaced by a reflective surface which is located a microscopic distance above the would-be classical horizon. Instead of an absorbing black hole, the resulting horizonless spacetime describes a reflective exotic compact object. Motivated by this intriguing prediction, in the present paper we explore the physical properties of exotic compact objects which are linearly coupled to stationary bound-state massive scalar field configurations. In particular, solving the Klein-Gordon wave equation for a stationary scalar field of proper mass $\mu$ and spheroidal harmonic indices $(l,m)$ in the background of a rapidly-rotating exotic compact object of mass $M$ and angular momentum $J=Ma$, we derive a compact analytical formula for the {\it discrete} radii $\{r_{\text{c}}(\mu,l,m,M,a;n)\}$ of the exotic compact objects which can support the stationary bound-state massive scalar field configurations. We confirm our analytical results by direct numerical computations. |
2207.01292 | Alfredo Bautista | A. Bautista, A. Ibort, J. Lafuente | L-extensions and L-boundary of conformal spacetimes | 39 pages, 6 figures | General Relativity and Gravitation, volume 50, article number: 153
(2018) | 10.1007/s10714-018-2479-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The notion of L-boundary, a new causal boundary proposed by R. Low based on
constructing a `sky at infinity' for any light ray, is discussed in detail. The
analysis of the notion of L-boundary will be done in the 3-dimensional
situation for the ease of presentation. The proposed notion of causal boundary
is intrinsically conformal and, as it will be proved in the paper, under
natural conditions provides a natural extension $\bar{M}$ of the given
spacetime $M$ with smooth boundary $\partial M = \bar{M} \backslash M$. The
extensions $\bar{M}$ of any conformal manifold $M$ constructed in this way are
characterised exclusively in terms of local properties at the boundary points.
Such extensions are called L-extensions and it is proved that, if they exist,
they are essentially unique. Finally it is shown that in the 3-dimensional
case, any L-extension is equivalent to the canonical extension obtained by
using the L-boundary of the manifold.
| [
{
"created": "Mon, 4 Jul 2022 09:47:23 GMT",
"version": "v1"
}
] | 2022-07-05 | [
[
"Bautista",
"A.",
""
],
[
"Ibort",
"A.",
""
],
[
"Lafuente",
"J.",
""
]
] | The notion of L-boundary, a new causal boundary proposed by R. Low based on constructing a `sky at infinity' for any light ray, is discussed in detail. The analysis of the notion of L-boundary will be done in the 3-dimensional situation for the ease of presentation. The proposed notion of causal boundary is intrinsically conformal and, as it will be proved in the paper, under natural conditions provides a natural extension $\bar{M}$ of the given spacetime $M$ with smooth boundary $\partial M = \bar{M} \backslash M$. The extensions $\bar{M}$ of any conformal manifold $M$ constructed in this way are characterised exclusively in terms of local properties at the boundary points. Such extensions are called L-extensions and it is proved that, if they exist, they are essentially unique. Finally it is shown that in the 3-dimensional case, any L-extension is equivalent to the canonical extension obtained by using the L-boundary of the manifold. |
gr-qc/0205108 | Carlo Rovelli | Carlo Rovelli, Simone Speziale | Reconcile Planck-scale discreteness and the Lorentz-Fitzgerald
contraction | 12 pages, 3 figures | Phys.Rev. D67 (2003) 064019 | 10.1103/PhysRevD.67.064019 | null | gr-qc | null | A Planck-scale minimal observable length appears in many approaches to
quantum gravity. It is sometimes argued that this minimal length might conflict
with Lorentz invariance, because a boosted observer could see the minimal
length further Lorentz contracted. We show that this is not the case within
loop quantum gravity. In loop quantum gravity the minimal length (more
precisely, minimal area) does not appear as a fixed property of geometry, but
rather as the minimal (nonzero) eigenvalue of a quantum observable. The boosted
observer can see the same observable spectrum, with the same minimal area. What
changes continuously in the boost transformation is not the value of the
minimal length: it is the probability distribution of seeing one or the other
of the discrete eigenvalues of the area. We discuss several difficulties
associated with boosts and area measurement in quantum gravity. We compute the
transformation of the area operator under a local boost, propose an explicit
expression for the generator of local boosts and give the conditions under
which its action is unitary.
| [
{
"created": "Sat, 25 May 2002 13:51:52 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Rovelli",
"Carlo",
""
],
[
"Speziale",
"Simone",
""
]
] | A Planck-scale minimal observable length appears in many approaches to quantum gravity. It is sometimes argued that this minimal length might conflict with Lorentz invariance, because a boosted observer could see the minimal length further Lorentz contracted. We show that this is not the case within loop quantum gravity. In loop quantum gravity the minimal length (more precisely, minimal area) does not appear as a fixed property of geometry, but rather as the minimal (nonzero) eigenvalue of a quantum observable. The boosted observer can see the same observable spectrum, with the same minimal area. What changes continuously in the boost transformation is not the value of the minimal length: it is the probability distribution of seeing one or the other of the discrete eigenvalues of the area. We discuss several difficulties associated with boosts and area measurement in quantum gravity. We compute the transformation of the area operator under a local boost, propose an explicit expression for the generator of local boosts and give the conditions under which its action is unitary. |
2105.09372 | Jacek Tafel | Jacek Tafel | The Einstein equations and multipole moments at null infinity | 19 pages | null | 10.1088/1361-6382/ac6b77 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider vacuum metrics admitting conformal compactification which is
smooth up to the scri $\mathscr{I^+}$. We write metric in the Bondi-Sachs form
and expand it into power series in the inverse affine distance $1/r$. Like in
the case of the luminosity distance, given the news tensor and initial data for
a part of metric the Einstein equations define coefficients of the series in a
recursive way. This is also true in the stationary case however now the news
tensor vanishes and the role of initial data is taken by multipole moments
which are equivalent to moments of Thorne. We find an approximate form of
metric and show that in the case of vanishing mass the mass dipole may be
different from zero. Then the known result about the Kerr like behaviour of a
stationary metric is violated. Finally we find an approximate (up to the
quadrupole moment) Bondi-Sachs form of the Kerr metric.
| [
{
"created": "Wed, 19 May 2021 19:27:22 GMT",
"version": "v1"
},
{
"created": "Mon, 31 May 2021 20:41:01 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Nov 2021 08:16:49 GMT",
"version": "v3"
},
{
"created": "Thu, 7 Apr 2022 18:43:19 GMT",
"version": "v4"
}
] | 2022-06-01 | [
[
"Tafel",
"Jacek",
""
]
] | We consider vacuum metrics admitting conformal compactification which is smooth up to the scri $\mathscr{I^+}$. We write metric in the Bondi-Sachs form and expand it into power series in the inverse affine distance $1/r$. Like in the case of the luminosity distance, given the news tensor and initial data for a part of metric the Einstein equations define coefficients of the series in a recursive way. This is also true in the stationary case however now the news tensor vanishes and the role of initial data is taken by multipole moments which are equivalent to moments of Thorne. We find an approximate form of metric and show that in the case of vanishing mass the mass dipole may be different from zero. Then the known result about the Kerr like behaviour of a stationary metric is violated. Finally we find an approximate (up to the quadrupole moment) Bondi-Sachs form of the Kerr metric. |
gr-qc/0003014 | Bahram Mashhoon | Bahram Mashhoon | Measurement Theory and General Relativity | LaTeX springer style lamu.cls, 2 figures, 16 pages, published in:
Black Holes: Theory and Observation: Proceedings of the 179th W.E. Heraeus
Seminar, held August 1997 in Bad Honnef, Germany. F.W. Hehl et al.(eds).
(Springer, Berlin Heidelberg 1998) | Lect.Notes Phys. 514 (1998) 269-284 | 10.1007/b13593 | null | gr-qc | null | The theory of measurement is employed to elucidate the physical basis of
general relativity. For measurements involving phenomena with intrinsic length
or time scales, such scales must in general be negligible compared to the
(translational and rotational) scales characteristic of the motion of the
observer. Thus general relativity is a consistent theory of coincidences so
long as these involve classical point particles and electromagnetic rays
(geometric optics). Wave optics is discussed and the limitations of the
standard theory in this regime are pointed out. A nonlocal theory of
accelerated observers is briefly described that is consistent with observation
and excludes the possibility of existence of a fundamental scalar field in
nature.
| [
{
"created": "Sun, 5 Mar 2000 23:29:12 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Mashhoon",
"Bahram",
""
]
] | The theory of measurement is employed to elucidate the physical basis of general relativity. For measurements involving phenomena with intrinsic length or time scales, such scales must in general be negligible compared to the (translational and rotational) scales characteristic of the motion of the observer. Thus general relativity is a consistent theory of coincidences so long as these involve classical point particles and electromagnetic rays (geometric optics). Wave optics is discussed and the limitations of the standard theory in this regime are pointed out. A nonlocal theory of accelerated observers is briefly described that is consistent with observation and excludes the possibility of existence of a fundamental scalar field in nature. |
1602.02378 | Alexander Zhidenko | Roman Konoplya, Luciano Rezzolla, and Alexander Zhidenko | General parametrization of axisymmetric black holes in metric theories
of gravity | 17 pages, to be published in PRD | Phys. Rev. D 93, 064015 (2016) | 10.1103/PhysRevD.93.064015 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following previous work of ours in spherical symmetry, we here propose a new
parametric framework to describe the spacetime of axisymmetric black holes in
generic metric theories of gravity. In this case, the metric components are
functions of both the radial and the polar angular coordinates, forcing a
double expansion to obtain a generic axisymmetric metric expression. In
particular, we use a continued-fraction expansion in terms of a compactified
radial coordinate to express the radial dependence, while we exploit a Taylor
expansion in terms of the cosine of the polar angle for the polar dependence.
These choices lead to a superior convergence in the radial direction and to an
exact limit on the equatorial plane. As a validation of our approach, we build
parametrized representations of Kerr, rotating dilaton, and
Einstein-dilaton-Gauss-Bonnet black holes. The match is already very good at
lowest order in the expansion and improves as new orders are added. We expect a
similar behavior for any stationary and axisymmetric black-hole metric.
| [
{
"created": "Sun, 7 Feb 2016 14:56:50 GMT",
"version": "v1"
}
] | 2016-03-11 | [
[
"Konoplya",
"Roman",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Zhidenko",
"Alexander",
""
]
] | Following previous work of ours in spherical symmetry, we here propose a new parametric framework to describe the spacetime of axisymmetric black holes in generic metric theories of gravity. In this case, the metric components are functions of both the radial and the polar angular coordinates, forcing a double expansion to obtain a generic axisymmetric metric expression. In particular, we use a continued-fraction expansion in terms of a compactified radial coordinate to express the radial dependence, while we exploit a Taylor expansion in terms of the cosine of the polar angle for the polar dependence. These choices lead to a superior convergence in the radial direction and to an exact limit on the equatorial plane. As a validation of our approach, we build parametrized representations of Kerr, rotating dilaton, and Einstein-dilaton-Gauss-Bonnet black holes. The match is already very good at lowest order in the expansion and improves as new orders are added. We expect a similar behavior for any stationary and axisymmetric black-hole metric. |
1304.5205 | Vasudev Shyam S | Vasudev Shyam | On the Geometric Quantization of Canonical Gravity | 12 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the hardest problems to tackle in the dynamics of canonical approaches
to quantum gravity is that of the Hamiltonian constraint. We investigate said
problem in the context of formal geometric quantization. We study the
implications of the non uniqueness in the choice of the vector field which
satisfies the presymplectic equation for the Hamiltonian constraint, and study
the implication of the same in the quantization of the theory. Our aim is to
show that this non uniqueness in the choice of said vector field, which really
stems from refoliation invariance leads to a very ambiguous notion of quantum
evolution. We then investigate the case of a theory where the problem of the
Hamiltonian constraint has been dealt with at the classical level, namely Shape
Dynamics, and attempt to derive a time dependent Schrodinger equation for the
quantum dynamics of this theory.
| [
{
"created": "Wed, 17 Apr 2013 15:13:23 GMT",
"version": "v1"
}
] | 2013-04-19 | [
[
"Shyam",
"Vasudev",
""
]
] | One of the hardest problems to tackle in the dynamics of canonical approaches to quantum gravity is that of the Hamiltonian constraint. We investigate said problem in the context of formal geometric quantization. We study the implications of the non uniqueness in the choice of the vector field which satisfies the presymplectic equation for the Hamiltonian constraint, and study the implication of the same in the quantization of the theory. Our aim is to show that this non uniqueness in the choice of said vector field, which really stems from refoliation invariance leads to a very ambiguous notion of quantum evolution. We then investigate the case of a theory where the problem of the Hamiltonian constraint has been dealt with at the classical level, namely Shape Dynamics, and attempt to derive a time dependent Schrodinger equation for the quantum dynamics of this theory. |
gr-qc/0611039 | Thomas Sotiriou | Thomas P. Sotiriou, Theocharis A. Apostolatos | Multipole moments as a tool to infer from gravitational waves the
geometry around an axisymmetric body | Talk given by T. P. S. at Albert Einstein's Century International
Conference, Paris, France, 18-22 Jul 2005 | AIP Conf. Proc. 861, 756 (2006) | 10.1063/1.2399654 | null | gr-qc | null | A binary system, composed of a compact object orbiting around a massive
central body, will emit gravitational waves which will depend on the central
body's spacetime geometry. We expect that the gravitational wave observables
will somehow ``encode'' the information about the spacetime structure. On the
other hand, it has been known for some time that the geometry around an
axisymmetric body can be described by its (Geroch-Hansen) multipole moments.
Therefore one can speculate that using the multipole moments can prove to be a
helpful tool for extracting this information. We will try to demonstrate this
in this talk, following the procedure described by [F. D. Ryan, Phys. Rev. D
{\bf 52} 5707 (1995)] and [T. P. Sotiriou and T. A. Apostolatos, Phys. Rev. D
{\bf 71} 044005 (2005)].
| [
{
"created": "Mon, 6 Nov 2006 14:59:36 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sotiriou",
"Thomas P.",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | A binary system, composed of a compact object orbiting around a massive central body, will emit gravitational waves which will depend on the central body's spacetime geometry. We expect that the gravitational wave observables will somehow ``encode'' the information about the spacetime structure. On the other hand, it has been known for some time that the geometry around an axisymmetric body can be described by its (Geroch-Hansen) multipole moments. Therefore one can speculate that using the multipole moments can prove to be a helpful tool for extracting this information. We will try to demonstrate this in this talk, following the procedure described by [F. D. Ryan, Phys. Rev. D {\bf 52} 5707 (1995)] and [T. P. Sotiriou and T. A. Apostolatos, Phys. Rev. D {\bf 71} 044005 (2005)]. |
1903.10850 | Jeferson de Oliveira | E. Abdalla, B. Cuadros-Melgar, R. D. B. Fontana, Jeferson de Oliveira,
Eleftherios Papantonopoulos and A. B. Pavan | Instability of Reissner-Nordstr\"om-AdS black hole under perturbations
of a scalar field coupled to Einstein tensor | 18 pages, 6 figures | Phys. Rev. D 99, 104065 (2019) | 10.1103/PhysRevD.99.104065 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the instability of a Reissner-Nordstr\"om-AdS (RNAdS) black hole
under perturbations of a massive scalar field coupled to Einstein tensor.
Calculating the potential of the scalar perturbations we find that as the
strength of the coupling of the scalar to Einstein tensor is increasing, the
potential develops a negative well outside the black hole horizon, indicating
an instability of the background RNAdS. We then investigate the effect of this
coupling on the quasinormal modes. We find that there exists a critical value
of the coupling which triggers the instability of the RNAdS. We also find that
as the charge of the RNAdS is increased towards its extremal value, the
critical value of the derivative coupling is decreased.
| [
{
"created": "Tue, 26 Mar 2019 13:13:59 GMT",
"version": "v1"
}
] | 2019-06-06 | [
[
"Abdalla",
"E.",
""
],
[
"Cuadros-Melgar",
"B.",
""
],
[
"Fontana",
"R. D. B.",
""
],
[
"de Oliveira",
"Jeferson",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Pavan",
"A. B.",
""
]
] | We study the instability of a Reissner-Nordstr\"om-AdS (RNAdS) black hole under perturbations of a massive scalar field coupled to Einstein tensor. Calculating the potential of the scalar perturbations we find that as the strength of the coupling of the scalar to Einstein tensor is increasing, the potential develops a negative well outside the black hole horizon, indicating an instability of the background RNAdS. We then investigate the effect of this coupling on the quasinormal modes. We find that there exists a critical value of the coupling which triggers the instability of the RNAdS. We also find that as the charge of the RNAdS is increased towards its extremal value, the critical value of the derivative coupling is decreased. |
2304.08877 | Subhra Bhattacharya | Subhra Bhattacharya and Subhasis Nalui | Complexity factor Parametrization for Traversable Wormholes | Accepted for Publication at J. Math. Phys | null | 10.1063/5.0148762 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It is known that static traversable wormhole in Einstein gravity is supported
by matter that violates null energy conditions (NEC). Essentially such wormhole
will be characterised by a central throat with anisotropic matter lining the
throat that violates NEC. This in turn provides viable geometry for the
wormhole to sustain. In 2018, L. Herrera introduced a new classification for
spherically symmetric bodies called ``complexity factor". It was proposed that
a spherically symmetric non trivial geometry can be classified as complex or
non-complex based on the nature of the inhomogeneity and anisotropy of the
stress energy tensors with only homogeneous and isotropic matter distribution
leading to null complexity. Mathematically there was also another way of
obtaining zero complexity geometry. In this context since static traversable
wormhole by default is characterised by anisotropic and inhomogeneous matter
stress tensors, the question we answer is whether it is possible to obtain zero
complexity class of wormholes supported by exotic matter.
| [
{
"created": "Tue, 18 Apr 2023 10:10:42 GMT",
"version": "v1"
}
] | 2023-05-17 | [
[
"Bhattacharya",
"Subhra",
""
],
[
"Nalui",
"Subhasis",
""
]
] | It is known that static traversable wormhole in Einstein gravity is supported by matter that violates null energy conditions (NEC). Essentially such wormhole will be characterised by a central throat with anisotropic matter lining the throat that violates NEC. This in turn provides viable geometry for the wormhole to sustain. In 2018, L. Herrera introduced a new classification for spherically symmetric bodies called ``complexity factor". It was proposed that a spherically symmetric non trivial geometry can be classified as complex or non-complex based on the nature of the inhomogeneity and anisotropy of the stress energy tensors with only homogeneous and isotropic matter distribution leading to null complexity. Mathematically there was also another way of obtaining zero complexity geometry. In this context since static traversable wormhole by default is characterised by anisotropic and inhomogeneous matter stress tensors, the question we answer is whether it is possible to obtain zero complexity class of wormholes supported by exotic matter. |
1705.05244 | Olivier Minazzoli | Olivier Minazzoli, L\'eo Bernus, Agn\`es Fienga, Aur\'elien Hees,
Jacques Laskar, Vishnu Viswanathan | Universality of free fall versus ephemeris | To appear in the Proceedings of the 52th Rencontres de Moriond. 4
pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When a light scalar field with gravitational strength interacts with matter,
the weak equivalence principle is in general violated, leading for instance to
a violation of the universality of free fall. This has been known and tested
for a while. However, recent developments [Minazzoli & Hees, PRD 2016] showed
that a novel manifestation of the universality of free fall can appear in some
models. Here we discuss this new scenario and expose how we intend to constrain
it with INPOP ephemeris.
| [
{
"created": "Mon, 15 May 2017 15:42:28 GMT",
"version": "v1"
}
] | 2017-05-16 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Bernus",
"Léo",
""
],
[
"Fienga",
"Agnès",
""
],
[
"Hees",
"Aurélien",
""
],
[
"Laskar",
"Jacques",
""
],
[
"Viswanathan",
"Vishnu",
""
]
] | When a light scalar field with gravitational strength interacts with matter, the weak equivalence principle is in general violated, leading for instance to a violation of the universality of free fall. This has been known and tested for a while. However, recent developments [Minazzoli & Hees, PRD 2016] showed that a novel manifestation of the universality of free fall can appear in some models. Here we discuss this new scenario and expose how we intend to constrain it with INPOP ephemeris. |
1006.5088 | Edward Green | Dave Pandres, Jr | Gravitational and electroweak unification by replacing diffeomorphisms
with larger group | 28 pages, | Gen.Rel.Grav.41:2501-2528,2009 | 10.1007/s10714-009-0788-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The covariance group for general relativity, the diffeomorphisms, is replaced
by a group of coordinate transformations which contains the diffeomorphisms as
a proper subgroup. The larger group is defined by the assumption that all
observers will agree whether any given quantity is conserved. Alternatively,
and equivalently, it is defined by the assumption that all observers will agree
that the general relativistic wave equation describes the propagation of light.
Thus, the group replacement is analogous to the replacement of the Lorentz
group by the diffeomorphisms that led Einstein from special relativity to
general relativity, and is also consistent with the assumption of constant
light velocity that led him to special relativity. The enlarged covariance
group leads to a non-commutative geometry based not on a manifold, but on a
nonlocal space in which paths, rather than points, are the most primitive
invariant entities. This yields a theory which unifies the gravitational and
electroweak interactions. The theory contains no adjustable parameters, such as
those that are chosen arbitrarily in the standard model.
| [
{
"created": "Sat, 26 Jun 2010 01:05:27 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Pandres,",
"Dave",
"Jr"
]
] | The covariance group for general relativity, the diffeomorphisms, is replaced by a group of coordinate transformations which contains the diffeomorphisms as a proper subgroup. The larger group is defined by the assumption that all observers will agree whether any given quantity is conserved. Alternatively, and equivalently, it is defined by the assumption that all observers will agree that the general relativistic wave equation describes the propagation of light. Thus, the group replacement is analogous to the replacement of the Lorentz group by the diffeomorphisms that led Einstein from special relativity to general relativity, and is also consistent with the assumption of constant light velocity that led him to special relativity. The enlarged covariance group leads to a non-commutative geometry based not on a manifold, but on a nonlocal space in which paths, rather than points, are the most primitive invariant entities. This yields a theory which unifies the gravitational and electroweak interactions. The theory contains no adjustable parameters, such as those that are chosen arbitrarily in the standard model. |
1902.03869 | Andre Fuzfa | A. F\"uzfa | Interstellar travels aboard radiation-powered rockets | 18 pages, 11 figures ; Open Access | Phys. Rev. D 99, 104081 (2019) | 10.1103/PhysRevD.99.104081 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We model accelerated trips at high-velocity aboard light sails (beam-powered
propulsion in general) and radiation rockets (thrust by anisotropic emission of
radiation) in terms of Kinnersley's solution of general relativity and its
associated geodesics. The analysis of radiation rockets relativistic kinematics
shows that the true problem of interstellar travel is not really the amount of
propellant, nor the duration of the trip but rather its tremendous energy cost.
Indeed, a flyby of Proxima Centauri with an ultralight gram-scale laser sail
would require the energy produced by a 1 GW power plant during about one day,
while more than 15 times the current world energy production would be required
for sending a 100 tons radiation rocket to the nearest star system. The
deformation of the local celestial sphere aboard radiation rockets is obtained
through the null geodesics of Kinnersley's spacetime in the Hamiltonian
formulation. It is shown how relativistic aberration and Doppler effect for the
accelerated traveller differ from their description in special relativity for
motion at constant velocity. We also show how our results could interestingly
be extended to extremely luminous events like the large amount of gravitational
waves emitted by binary black hole mergers.
| [
{
"created": "Mon, 11 Feb 2019 13:37:32 GMT",
"version": "v1"
},
{
"created": "Fri, 31 May 2019 19:37:43 GMT",
"version": "v2"
}
] | 2019-06-05 | [
[
"Füzfa",
"A.",
""
]
] | We model accelerated trips at high-velocity aboard light sails (beam-powered propulsion in general) and radiation rockets (thrust by anisotropic emission of radiation) in terms of Kinnersley's solution of general relativity and its associated geodesics. The analysis of radiation rockets relativistic kinematics shows that the true problem of interstellar travel is not really the amount of propellant, nor the duration of the trip but rather its tremendous energy cost. Indeed, a flyby of Proxima Centauri with an ultralight gram-scale laser sail would require the energy produced by a 1 GW power plant during about one day, while more than 15 times the current world energy production would be required for sending a 100 tons radiation rocket to the nearest star system. The deformation of the local celestial sphere aboard radiation rockets is obtained through the null geodesics of Kinnersley's spacetime in the Hamiltonian formulation. It is shown how relativistic aberration and Doppler effect for the accelerated traveller differ from their description in special relativity for motion at constant velocity. We also show how our results could interestingly be extended to extremely luminous events like the large amount of gravitational waves emitted by binary black hole mergers. |
0706.2543 | Tolga Birkandan | T. Birkandan, M. Hortacsu | Dirac Equation in the Background of the Nutku Helicoid Metric | 16 pages, 1 figure, TeX file using boxedeps. Replaced by the revised
version | J.Math.Phys.48:092301,2007 | 10.1063/1.2785124 | null | gr-qc math-ph math.MP | null | We study the solutions of the Dirac equation in the background of the Nutku
helicoid metric. This metric has curvature singularities, which necessitates
imposing a boundary to exclude this point. We use the Atiyah-Patodi-Singer non
local spectral boundary conditions for both the four and the five dimensional
manifolds.
| [
{
"created": "Mon, 18 Jun 2007 07:56:46 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2007 06:50:04 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Birkandan",
"T.",
""
],
[
"Hortacsu",
"M.",
""
]
] | We study the solutions of the Dirac equation in the background of the Nutku helicoid metric. This metric has curvature singularities, which necessitates imposing a boundary to exclude this point. We use the Atiyah-Patodi-Singer non local spectral boundary conditions for both the four and the five dimensional manifolds. |
1501.06540 | Christian Boehmer | Christian G. Boehmer, Nicola Tamanini, Matthew Wright | Interacting quintessence from a variational approach Part I: algebraic
couplings | 29 pages, 12 figures; updated and slightly extended, matches
published version | Phys. Rev. D 91, 123002 (2015) | 10.1103/PhysRevD.91.123002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new approach to build models of quintessence interacting with
dark or baryonic matter. We use a variational approach for relativistic fluids
to realize an effective description of matter fields at the Lagrangian level.
The coupling is introduced directly in the action by considering a single
function mixing the dynamical degrees of freedom of the theory. The resulting
gravitational field equations are derived by variations with respect to the
independent variables. New interesting phenomenology can be obtained at both
small scales, where new screening mechanisms for scalar fields can be realized,
and large scales, where one finds an original and rich class of interacting
quintessence models. The background cosmology of two of these models is studied
in detail using dynamical system techniques. We find a variety of interesting
results: for instance, these models contain dark energy dominated late time
attractors and scaling solutions, both with early time matter dominated epochs
and a possible inflationary origin. In general this new approach provides the
starting point for future in depth studies on new interacting quintessence
models.
| [
{
"created": "Mon, 26 Jan 2015 19:48:28 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2015 11:10:38 GMT",
"version": "v2"
}
] | 2015-06-10 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Tamanini",
"Nicola",
""
],
[
"Wright",
"Matthew",
""
]
] | We present a new approach to build models of quintessence interacting with dark or baryonic matter. We use a variational approach for relativistic fluids to realize an effective description of matter fields at the Lagrangian level. The coupling is introduced directly in the action by considering a single function mixing the dynamical degrees of freedom of the theory. The resulting gravitational field equations are derived by variations with respect to the independent variables. New interesting phenomenology can be obtained at both small scales, where new screening mechanisms for scalar fields can be realized, and large scales, where one finds an original and rich class of interacting quintessence models. The background cosmology of two of these models is studied in detail using dynamical system techniques. We find a variety of interesting results: for instance, these models contain dark energy dominated late time attractors and scaling solutions, both with early time matter dominated epochs and a possible inflationary origin. In general this new approach provides the starting point for future in depth studies on new interacting quintessence models. |
2009.03003 | Tobias Mistele | Tobias Mistele | Three problems of superfluid dark matter and their solution | 34 pages, 5 figures, published version | JCAP 2101 (2021) 025 | 10.1088/1475-7516/2021/01/025 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In superfluid dark matter (SFDM), the phonon field plays a double role: It
carries the superfluid's energy density and it mediates the MOND-like phonon
force. We show that these two roles are in tension with each other on galactic
scales: A MOND-like phonon force is in tension with a superfluid in equilibrium
and with a significant superfluid energy density. To avoid these tensions, we
propose a model where the two roles are split between two different fields.
This also allows us to solve a stability problem in a more elegant way than
standard SFDM. We argue that the standard estimates for the size of a galaxy's
superfluid core need to be revisited.
| [
{
"created": "Mon, 7 Sep 2020 10:37:17 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2020 10:59:46 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jan 2021 11:43:40 GMT",
"version": "v3"
}
] | 2021-01-18 | [
[
"Mistele",
"Tobias",
""
]
] | In superfluid dark matter (SFDM), the phonon field plays a double role: It carries the superfluid's energy density and it mediates the MOND-like phonon force. We show that these two roles are in tension with each other on galactic scales: A MOND-like phonon force is in tension with a superfluid in equilibrium and with a significant superfluid energy density. To avoid these tensions, we propose a model where the two roles are split between two different fields. This also allows us to solve a stability problem in a more elegant way than standard SFDM. We argue that the standard estimates for the size of a galaxy's superfluid core need to be revisited. |
1603.06983 | Mariam Bouhmadi-Lopez | Mariam Bouhmadi-L\'opez, Jo\~ao Morais, Alexander Zhuk | The late Universe with non-linear interaction in the dark sector: the
coincidence problem | 24 pages, no figures. Conclusions extended and references updated.
Version accepted in Physics of the Dark Universe | Phys.Dark Univ. 14 (2016) 11-20 | 10.1016/j.dark.2016.08.001 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Universe at the late stage of its evolution and deep inside the
cell of uniformity. At such a scale the Universe is highly inhomogeneous and
filled with discretely distributed inhomogeneities in the form of galaxies and
groups of galaxies. As a matter source, we consider dark matter (DM) and dark
energy (DE) with a non-linear interaction $Q = 3\mathcal{H}\gamma
\bar\varepsilon_{\mathrm{DE}} \bar\varepsilon_{\mathrm{DM}} /
(\bar\varepsilon_{\mathrm{DE}} + \bar\varepsilon_{\mathrm{DM}})$, where
$\gamma$ is a constant. We assume that DM is pressureless and DE has a constant
equation of state parameter $w$. In the considered model, the energy densities
of the dark sector components present a scaling behaviour with
$\bar\varepsilon_{\mathrm{DM}} / \bar\varepsilon_{\mathrm{DE}} \sim \left({a_0}
/ {a} \right)^{-3(w+\gamma)}$. We investigate the possibility that the
perturbations of DM and DE, which are interacting among themselves, could be
coupled to the galaxies with the former being concentrated around them. To
carry our analysis, we consider the theory of scalar perturbations (within the
mechanical approach), and obtain the sets of parameters $(w,\gamma)$ which do
not contradict it. We conclude that two sets: $(w=-2/3,\gamma=1/3)$ and
$(w=-1,\gamma=1/3)$ are of special interest. First, the energy densities of DM
and DE on these cases are concentrated around galaxies confirming that they are
coupled fluids. Second, we show that for both of them, the coincidence problem
is less severe than in the standard $\Lambda$CDM. Third, the set
$(w=-1,\gamma=1/3)$ is within the observational constraints. Finally, we also
obtain an expression for the gravitational potential in the considered model.
| [
{
"created": "Tue, 22 Mar 2016 21:06:08 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jul 2016 11:09:42 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Aug 2016 13:22:42 GMT",
"version": "v3"
}
] | 2016-08-25 | [
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Morais",
"João",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study the Universe at the late stage of its evolution and deep inside the cell of uniformity. At such a scale the Universe is highly inhomogeneous and filled with discretely distributed inhomogeneities in the form of galaxies and groups of galaxies. As a matter source, we consider dark matter (DM) and dark energy (DE) with a non-linear interaction $Q = 3\mathcal{H}\gamma \bar\varepsilon_{\mathrm{DE}} \bar\varepsilon_{\mathrm{DM}} / (\bar\varepsilon_{\mathrm{DE}} + \bar\varepsilon_{\mathrm{DM}})$, where $\gamma$ is a constant. We assume that DM is pressureless and DE has a constant equation of state parameter $w$. In the considered model, the energy densities of the dark sector components present a scaling behaviour with $\bar\varepsilon_{\mathrm{DM}} / \bar\varepsilon_{\mathrm{DE}} \sim \left({a_0} / {a} \right)^{-3(w+\gamma)}$. We investigate the possibility that the perturbations of DM and DE, which are interacting among themselves, could be coupled to the galaxies with the former being concentrated around them. To carry our analysis, we consider the theory of scalar perturbations (within the mechanical approach), and obtain the sets of parameters $(w,\gamma)$ which do not contradict it. We conclude that two sets: $(w=-2/3,\gamma=1/3)$ and $(w=-1,\gamma=1/3)$ are of special interest. First, the energy densities of DM and DE on these cases are concentrated around galaxies confirming that they are coupled fluids. Second, we show that for both of them, the coincidence problem is less severe than in the standard $\Lambda$CDM. Third, the set $(w=-1,\gamma=1/3)$ is within the observational constraints. Finally, we also obtain an expression for the gravitational potential in the considered model. |
gr-qc/0610040 | Bogusz Kinasiewicz | Bogusz Kinasiewicz, Patryk Mach | From polytropic to barotropic perfect fluids in general-relativistic
hydrodynamics | 22 pages. To appear in Acta Phys. Pol. B | Acta Phys.Polon. B38 (2007) 39-60 | null | null | gr-qc | null | Two general-relativistic hydrodynamical models are considered: a model of
self-gravitating static configurations of perfect fluid and a model of steady
accretion of fluid onto a black hole. We generalise analytic results obtained
for the original polytropic versions of these models onto a wider class of
barotropic equations of state. The knowledge about the polytropic solutions is
used to establish bounds on certain characteristic quantities appearing in both
cases.
| [
{
"created": "Tue, 10 Oct 2006 06:56:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kinasiewicz",
"Bogusz",
""
],
[
"Mach",
"Patryk",
""
]
] | Two general-relativistic hydrodynamical models are considered: a model of self-gravitating static configurations of perfect fluid and a model of steady accretion of fluid onto a black hole. We generalise analytic results obtained for the original polytropic versions of these models onto a wider class of barotropic equations of state. The knowledge about the polytropic solutions is used to establish bounds on certain characteristic quantities appearing in both cases. |
1408.6375 | Vladimir Khatsymovsky | V.M. Khatsymovsky | Some minisuperspace model for the Faddeev formulation of gravity | 14 pages, 3 figures, to appear in Mod. Phys. Lett. A | Mod. Phys. Lett. A, Vol. 29, No. 27 (2014) 1450141 | 10.1142/S0217732314501417 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Faddeev formulation of general relativity in which the metric is
composed of ten vector fields or a $4 \times 10$ tetrad. This formulation
reduces to the usual general relativity upon partial use of the field
equations.
A distinctive feature of the Faddeev action is its finiteness on the
discontinuous fields. This allows to introduce its minisuperspace formulation
where the vector fields are constant everywhere on ${\rm I \hspace{-3pt} R}^4$
with exception of a measure zero set (the piecewise constant fields). The
fields are parameterized by their constant values {\it independently} chosen
in, e. g., the 4-simplices or, say, parallelepipeds into which ${\rm I
\hspace{-3pt} R}^4$ can be decomposed. The form of the action for the vector
fields of this type is found.
We also consider the piecewise constant vector fields approximating the fixed
smooth ones. We check that if the regions in which the vector fields are
constant are made arbitrarily small, the minisuperspace action and eqs of
motion tend to the continuum Faddeev ones.
| [
{
"created": "Wed, 27 Aug 2014 10:19:39 GMT",
"version": "v1"
}
] | 2014-08-29 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | We consider Faddeev formulation of general relativity in which the metric is composed of ten vector fields or a $4 \times 10$ tetrad. This formulation reduces to the usual general relativity upon partial use of the field equations. A distinctive feature of the Faddeev action is its finiteness on the discontinuous fields. This allows to introduce its minisuperspace formulation where the vector fields are constant everywhere on ${\rm I \hspace{-3pt} R}^4$ with exception of a measure zero set (the piecewise constant fields). The fields are parameterized by their constant values {\it independently} chosen in, e. g., the 4-simplices or, say, parallelepipeds into which ${\rm I \hspace{-3pt} R}^4$ can be decomposed. The form of the action for the vector fields of this type is found. We also consider the piecewise constant vector fields approximating the fixed smooth ones. We check that if the regions in which the vector fields are constant are made arbitrarily small, the minisuperspace action and eqs of motion tend to the continuum Faddeev ones. |
2407.06270 | William Lamb | William G. Lamb, Stephen R. Taylor | Spectral Variance in a Stochastic Gravitational-Wave Background From a
Binary Population | 8 pages, 3 figures. Published in ApJL | ApJL 971 L10 (2024) | 10.3847/2041-8213/ad654a | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | A population of compact object binaries emitting gravitational waves that are
not individually resolvable will form a stochastic gravitational wave signal.
While the expected spectrum over population realizations is well known from
Phinney (2001), its higher order moments have not been fully studied before or
computed in the case of arbitrary binary evolution. We calculate analytic
scaling relationships as a function of gravitational-wave frequency for the
statistical variance, skewness, and kurtosis of a stochastic gravitational-wave
signal over population realizations due to finite source effects. If the time
derivative of the binary orbital frequency can be expressed as a power-law in
frequency, we find that these moment quantities also take the form of power-law
relationships. We also develop a numerical population synthesis framework
against which we compare our analytic results, finding excellent agreement.
These new scaling relationships provide physical context to understanding
spectral fluctuations in a gravitational-wave background signal and may provide
additional information that can aid in explaining the origin of the
nanohertz-frequency signal observed by pulsar timing array campaigns.
| [
{
"created": "Mon, 8 Jul 2024 18:00:04 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jul 2024 15:19:00 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Aug 2024 16:22:31 GMT",
"version": "v3"
}
] | 2024-08-06 | [
[
"Lamb",
"William G.",
""
],
[
"Taylor",
"Stephen R.",
""
]
] | A population of compact object binaries emitting gravitational waves that are not individually resolvable will form a stochastic gravitational wave signal. While the expected spectrum over population realizations is well known from Phinney (2001), its higher order moments have not been fully studied before or computed in the case of arbitrary binary evolution. We calculate analytic scaling relationships as a function of gravitational-wave frequency for the statistical variance, skewness, and kurtosis of a stochastic gravitational-wave signal over population realizations due to finite source effects. If the time derivative of the binary orbital frequency can be expressed as a power-law in frequency, we find that these moment quantities also take the form of power-law relationships. We also develop a numerical population synthesis framework against which we compare our analytic results, finding excellent agreement. These new scaling relationships provide physical context to understanding spectral fluctuations in a gravitational-wave background signal and may provide additional information that can aid in explaining the origin of the nanohertz-frequency signal observed by pulsar timing array campaigns. |
2211.11868 | Armin Van De Venn | Armin van de Venn, David Vasak, Johannes Kirsch, J\"urgen Struckmeier | Torsional dark energy in quadratic gauge gravity | 11 pages, 3 figures; updated to published version | Eur. Phys. J. C 83, 288 (2023) | 10.1140/epjc/s10052-023-11397-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Covariant Canonical Gauge theory of Gravity (CCGG) is a gauge field
formulation of gravity which a priori includes non-metricity and torsion. It
extends the Lagrangian of Einstein's theory of general relativity by terms at
least quadratic in the Riemann-Cartan tensor. This paper investigates the
implications of metric compatible CCGG on cosmological scales. For a totally
anti-symmetric torsion tensor we derive the resulting equations of motion in a
Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe. In the limit of a
vanishing quadratic Riemann-Cartan term, the arising modifications of the
Friedmann equations are shown to be equivalent to spatial curvature.
Furthermore, the modified Friedmann equations are investigated in detail in the
early and late times of the Universe's history. It is demonstrated that in
addition to the standard $\Lambda$CDM behaviour of the scale factor, there
exist novel time dependencies, emerging due to the presence of torsion and the
quadratic Riemann-Cartan term. Finally, at late times, we present how the
accelerated expansion of the Universe can be understood as a geometric effect
of spacetime through torsion, rendering the introduction of a cosmological
constant redundant. In such a scenario it is possible to compute an expected
value for the parameters of the postulated gravitational Hamiltonian/Lagrangian
and to provide a lower bound on the vacuum energy of matter.
| [
{
"created": "Mon, 21 Nov 2022 21:42:27 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Nov 2022 13:39:00 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Apr 2023 11:08:42 GMT",
"version": "v3"
}
] | 2023-04-13 | [
[
"van de Venn",
"Armin",
""
],
[
"Vasak",
"David",
""
],
[
"Kirsch",
"Johannes",
""
],
[
"Struckmeier",
"Jürgen",
""
]
] | The Covariant Canonical Gauge theory of Gravity (CCGG) is a gauge field formulation of gravity which a priori includes non-metricity and torsion. It extends the Lagrangian of Einstein's theory of general relativity by terms at least quadratic in the Riemann-Cartan tensor. This paper investigates the implications of metric compatible CCGG on cosmological scales. For a totally anti-symmetric torsion tensor we derive the resulting equations of motion in a Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe. In the limit of a vanishing quadratic Riemann-Cartan term, the arising modifications of the Friedmann equations are shown to be equivalent to spatial curvature. Furthermore, the modified Friedmann equations are investigated in detail in the early and late times of the Universe's history. It is demonstrated that in addition to the standard $\Lambda$CDM behaviour of the scale factor, there exist novel time dependencies, emerging due to the presence of torsion and the quadratic Riemann-Cartan term. Finally, at late times, we present how the accelerated expansion of the Universe can be understood as a geometric effect of spacetime through torsion, rendering the introduction of a cosmological constant redundant. In such a scenario it is possible to compute an expected value for the parameters of the postulated gravitational Hamiltonian/Lagrangian and to provide a lower bound on the vacuum energy of matter. |
gr-qc/9405003 | Arthur Wasserman | J. A. Smoller and A. G. Wasserman | Limiting Behavior of Solutions to the Einstein-Yang/Mills Equations | 2 pages, um5941 | Physica D93:123-136,1996 | 10.1016/0167-2789(95)00291-X | null | gr-qc | null | The ADM masses of particle-like solutions to the Einstein-Yang/Mills
Equations tend to 2 as the number of nodes of the solutions increases. The same
result is true for black hole solutions with event horizon less than 1. For
event horizon $\rho > 1$ the ADM masses converge to $\rho + \rho^{-1} .$ These
statements extend and correct ``An Investigation at the Limiting Behavior of
Particle-Like Solutions to the Einstein-Yang/Mills Equations and a New black
Hole Solutions'', by J. A. Smoller and A. G. Wasserman, in Comm. Math. Phys.,
161, 365-389, (1994).
| [
{
"created": "Mon, 2 May 1994 15:41:35 GMT",
"version": "v1"
}
] | 2015-08-28 | [
[
"Smoller",
"J. A.",
""
],
[
"Wasserman",
"A. G.",
""
]
] | The ADM masses of particle-like solutions to the Einstein-Yang/Mills Equations tend to 2 as the number of nodes of the solutions increases. The same result is true for black hole solutions with event horizon less than 1. For event horizon $\rho > 1$ the ADM masses converge to $\rho + \rho^{-1} .$ These statements extend and correct ``An Investigation at the Limiting Behavior of Particle-Like Solutions to the Einstein-Yang/Mills Equations and a New black Hole Solutions'', by J. A. Smoller and A. G. Wasserman, in Comm. Math. Phys., 161, 365-389, (1994). |
2202.02229 | Farook Rahaman | Mofazzal Azam, M Sami and Farook Rahaman | A note on shock wave in the dark matter medium | 4 pages. Submitted in Phys.Lett.B on 25.11.21 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Employing Newton's stellar balance equation and using the flat rotation
velocity of satellite galaxies, we have found the velocity of sound in the dark
matter medium. What is interesting is that the velocity of satellite galaxies
is very much larger than the velocity of sound in the dark matter medium. This
indicates that there will be shock wave in the dark matter medium due to the
supersonic movement of satellite galaxies.
| [
{
"created": "Wed, 2 Feb 2022 19:42:03 GMT",
"version": "v1"
}
] | 2022-02-07 | [
[
"Azam",
"Mofazzal",
""
],
[
"Sami",
"M",
""
],
[
"Rahaman",
"Farook",
""
]
] | Employing Newton's stellar balance equation and using the flat rotation velocity of satellite galaxies, we have found the velocity of sound in the dark matter medium. What is interesting is that the velocity of satellite galaxies is very much larger than the velocity of sound in the dark matter medium. This indicates that there will be shock wave in the dark matter medium due to the supersonic movement of satellite galaxies. |
1305.6933 | Yi-Zen Chu | Yi-Zen Chu | A Line Source In Minkowski For The de Sitter Spacetime Scalar Green's
Function: Massless Minimally Coupled Case | 27 pages, 1 figure. v3: The 1/N_0 and the sum over eigenvectors in
the general formula, eq. (9), is not needed; results are otherwise unaltered.
v4: Abstract, introduction and justification of general formula (eq. (9)) are
revised, thanks to referee's input | null | 10.1063/1.4895506 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the desire to understand the causal structure of physical
signals produced in curved spacetimes -- particularly around black holes -- we
show how, for certain classes of geometries, one might obtain its retarded or
advanced minimally coupled massless scalar Green's function by using the
corresponding Green's functions in the higher dimensional Minkowski spacetime
where it is embedded. Analogous statements hold for certain classes of curved
Riemannian spaces, with positive definite metrics, which may be embedded in
higher dimensional Euclidean spaces. The general formula is applied to $(d \geq
2)$-dimensional de Sitter spacetime, and the scalar Green's function is
demonstrated to be sourced by a line emanating infinitesimally close to the
origin of the ambient $(d+1)$-dimensional Minkowski spacetime and piercing
orthogonally through the de Sitter hyperboloids of all finite sizes. This
method does not require solving the de Sitter wave equation directly. Only the
zero mode solution to an ordinary differential equation, the "wave equation"
perpendicular to the hyperboloid -- followed by a one dimensional integral --
needs to be evaluated. A topological obstruction to the general construction is
also discussed by utilizing it to derive a generalized Green's function of the
Laplacian on the $(d \geq 2)$-dimensional sphere.
| [
{
"created": "Wed, 29 May 2013 20:00:13 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jun 2013 20:00:02 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Oct 2013 19:39:14 GMT",
"version": "v3"
},
{
"created": "Fri, 5 Sep 2014 04:21:24 GMT",
"version": "v4"
}
] | 2015-06-16 | [
[
"Chu",
"Yi-Zen",
""
]
] | Motivated by the desire to understand the causal structure of physical signals produced in curved spacetimes -- particularly around black holes -- we show how, for certain classes of geometries, one might obtain its retarded or advanced minimally coupled massless scalar Green's function by using the corresponding Green's functions in the higher dimensional Minkowski spacetime where it is embedded. Analogous statements hold for certain classes of curved Riemannian spaces, with positive definite metrics, which may be embedded in higher dimensional Euclidean spaces. The general formula is applied to $(d \geq 2)$-dimensional de Sitter spacetime, and the scalar Green's function is demonstrated to be sourced by a line emanating infinitesimally close to the origin of the ambient $(d+1)$-dimensional Minkowski spacetime and piercing orthogonally through the de Sitter hyperboloids of all finite sizes. This method does not require solving the de Sitter wave equation directly. Only the zero mode solution to an ordinary differential equation, the "wave equation" perpendicular to the hyperboloid -- followed by a one dimensional integral -- needs to be evaluated. A topological obstruction to the general construction is also discussed by utilizing it to derive a generalized Green's function of the Laplacian on the $(d \geq 2)$-dimensional sphere. |
gr-qc/0301083 | Gaetano Vilasi | F. Canfora and G. Vilasi | Spin-1 gravitational waves and their natural sources | 10 pages, latex | Phys.Lett. B585 (2004) 193-199 | 10.1016/j.physletb.2004.02.005 | null | gr-qc hep-th | null | Non-vacuum exact gravitational waves invariant for a non Abelian
two-dimensional Lie algebra generated by two Killing fields whose commutator is
of light type, are described. The polarization of these waves, already known
from previous works, is related to the sources. Non vacuum exact gravitational
waves admitting only one Killing field of light type are also discussed.
| [
{
"created": "Wed, 22 Jan 2003 09:07:31 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Feb 2004 21:00:12 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Canfora",
"F.",
""
],
[
"Vilasi",
"G.",
""
]
] | Non-vacuum exact gravitational waves invariant for a non Abelian two-dimensional Lie algebra generated by two Killing fields whose commutator is of light type, are described. The polarization of these waves, already known from previous works, is related to the sources. Non vacuum exact gravitational waves admitting only one Killing field of light type are also discussed. |
1908.05697 | Nikita Kolganov | A. O. Barvinsky and N. Kolganov | Inflation in generalized unimodular gravity | 13 pages, no figures | Phys. Rev. D 100, 123510 (2019) | 10.1103/PhysRevD.100.123510 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recently suggested generalized unimodular gravity theory, which was
originally put forward as a model of dark energy, can serve as a model of
cosmological inflation driven by the effective perfect fluid -- the dark purely
gravitational sector of the theory. Its excitations are scalar gravitons which
can generate, in the domain free from ghost and gradient instabilities, the red
tilted primordial power spectrum of CMB perturbations matching with
observations. The reconstruction of the parametric dependence of the action of
the theory in the early inflationary Universe is qualitatively sketched from
the cosmological data. The alternative possibilities of generating the
cosmological acceleration or quantum transition to the general relativistic
phase of the theory are also briefly discussed.
| [
{
"created": "Thu, 15 Aug 2019 18:14:42 GMT",
"version": "v1"
}
] | 2019-12-11 | [
[
"Barvinsky",
"A. O.",
""
],
[
"Kolganov",
"N.",
""
]
] | The recently suggested generalized unimodular gravity theory, which was originally put forward as a model of dark energy, can serve as a model of cosmological inflation driven by the effective perfect fluid -- the dark purely gravitational sector of the theory. Its excitations are scalar gravitons which can generate, in the domain free from ghost and gradient instabilities, the red tilted primordial power spectrum of CMB perturbations matching with observations. The reconstruction of the parametric dependence of the action of the theory in the early inflationary Universe is qualitatively sketched from the cosmological data. The alternative possibilities of generating the cosmological acceleration or quantum transition to the general relativistic phase of the theory are also briefly discussed. |
2006.08970 | Yuta Michimura Dr. | Yuta Michimura, Kentaro Komori, Yutaro Enomoto, Koji Nagano, Atsushi
Nishizawa, Eiichi Hirose, Matteo Leonardi, Eleonora Capocasa, Naoki Aritomi,
Yuhang Zhao, Raffaele Flaminio, Takafumi Ushiba, Tomohiro Yamada, Li-Wei Wei,
Hiroki Takeda, Satoshi Tanioka, Masaki Ando, Kazuhiro Yamamoto, Kazuhiro
Hayama, Sadakazu Haino, Kentaro Somiya | Prospects for improving the sensitivity of the cryogenic gravitational
wave detector KAGRA | 10 pages, 2 figures | Phys. Rev. D 102, 022008 (2020) | 10.1103/PhysRevD.102.022008 | JGW-P2011740 | gr-qc astro-ph.IM physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Upgrades to improve the sensitivity of gravitational wave detectors enable
more frequent detections and more precise source parameter estimation. Unlike
other advanced interferometric detectors such as Advanced LIGO and Advanced
Virgo, KAGRA requires different approach for the upgrade since it is the only
detector which employs cryogenic cooling of the test masses. In this paper, we
describe possible KAGRA upgrades with technologies focusing on different
detector bands, and compare the impacts on the detection of compact binary
coalescences. We show that either fivefold improvement in the $100
M_{\odot}$--$100 M_{\odot}$ binary black hole range, a factor of 1.3
improvement in the binary neutron star range, or a factor of 1.7 improvement in
the sky localization of binary neutron stars is well feasible with upgrades
that do not require changes in the existing cryogenic or vacuum infrastructure.
We also show that twofold broadband sensitivity improvement is possible by
applying multiple upgrades to the detector.
| [
{
"created": "Tue, 16 Jun 2020 07:54:48 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 2020 22:30:23 GMT",
"version": "v2"
}
] | 2020-07-28 | [
[
"Michimura",
"Yuta",
""
],
[
"Komori",
"Kentaro",
""
],
[
"Enomoto",
"Yutaro",
""
],
[
"Nagano",
"Koji",
""
],
[
"Nishizawa",
"Atsushi",
""
],
[
"Hirose",
"Eiichi",
""
],
[
"Leonardi",
"Matteo",
""
],
[
"Capocasa",
"Eleonora",
""
],
[
"Aritomi",
"Naoki",
""
],
[
"Zhao",
"Yuhang",
""
],
[
"Flaminio",
"Raffaele",
""
],
[
"Ushiba",
"Takafumi",
""
],
[
"Yamada",
"Tomohiro",
""
],
[
"Wei",
"Li-Wei",
""
],
[
"Takeda",
"Hiroki",
""
],
[
"Tanioka",
"Satoshi",
""
],
[
"Ando",
"Masaki",
""
],
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Hayama",
"Kazuhiro",
""
],
[
"Haino",
"Sadakazu",
""
],
[
"Somiya",
"Kentaro",
""
]
] | Upgrades to improve the sensitivity of gravitational wave detectors enable more frequent detections and more precise source parameter estimation. Unlike other advanced interferometric detectors such as Advanced LIGO and Advanced Virgo, KAGRA requires different approach for the upgrade since it is the only detector which employs cryogenic cooling of the test masses. In this paper, we describe possible KAGRA upgrades with technologies focusing on different detector bands, and compare the impacts on the detection of compact binary coalescences. We show that either fivefold improvement in the $100 M_{\odot}$--$100 M_{\odot}$ binary black hole range, a factor of 1.3 improvement in the binary neutron star range, or a factor of 1.7 improvement in the sky localization of binary neutron stars is well feasible with upgrades that do not require changes in the existing cryogenic or vacuum infrastructure. We also show that twofold broadband sensitivity improvement is possible by applying multiple upgrades to the detector. |
gr-qc/0608057 | Rolando Gaitan Deveras RGD | Rolando Gaitan and Frank Vera | GL(3,R) gauge theory of gravity coupled with an electromagnetic field | 5 pages, to appear in CIENCIA | null | null | null | gr-qc | null | Consistency of $GL(3,R)$ gauge theory of gravity coupled with an external
electromagnetic field, is studied. It is shown that possible restrictions on
Maxwell field can be avoided through introduction of auxiliary fields.
| [
{
"created": "Fri, 11 Aug 2006 00:56:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gaitan",
"Rolando",
""
],
[
"Vera",
"Frank",
""
]
] | Consistency of $GL(3,R)$ gauge theory of gravity coupled with an external electromagnetic field, is studied. It is shown that possible restrictions on Maxwell field can be avoided through introduction of auxiliary fields. |
1310.7395 | Bernard S. Kay | Bernard S. Kay (York) | Instability of enclosed horizons | 28 pages, 4 figures. Exposition improved. Paper now divided into
sections with endnotes in a separate section. Abstract rewritten, more
discussion, references added, typos corrected | General Relativity and Gravitation 47, 31 (2015) | 10.1007/s10714-015-1858-8 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that there are solutions to the scalar wave equation on 1+1
dimensional Minkowski space with finite energy tails which, if they reflect off
a uniformly accelerated mirror due to (say) Dirichlet boundary conditions on
it, develop an infinite stress-energy tensor on the mirror's Rindler horizon.
We also show that, in the presence of an image mirror in the opposite Rindler
wedge, suitable compactly supported arbitrarily small initial data on a
suitable initial surface will develop an arbitrarily large stress-energy scalar
near where the two horizons cross. Also, while there is a regular
Hartle-Hawking-Israel-like state for the quantum theory between these two
mirrors, there are coherent states built on it for which there are similar
singularities in the expectation value of the renormalized stress-energy
tensor. We conjecture that in other situations with analogous enclosed horizons
such as a (maximally extended) Schwarzschild black hole in equilibrium in a
(stationary spherical) box or the (maximally extended) Schwarzschild-AdS
spacetime, there will be similar stress-energy singularities and
almost-singularities -- leading to instability of the horizons when gravity is
switched on and matter and gravity perturbations are allowed for. All this
suggests it is incorrect to picture a black hole in equilibrium in a box or a
Schwarzschild-AdS black hole as extending beyond the past and future horizons
of a single Schwarzschild (/Schwarzschild-AdS) wedge. It would thus provide new
evidence for 't Hooft's brick wall model while seeming to invalidate the
picture in Maldacena's 'Eternal black holes in AdS'. It would thereby also
support the validity of the author's matter-gravity entanglement hypothesis and
of the paper 'Brick walls and AdS/CFT' by the author and Ort\'iz.
| [
{
"created": "Mon, 28 Oct 2013 12:06:56 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Oct 2013 01:44:47 GMT",
"version": "v2"
},
{
"created": "Thu, 22 May 2014 15:28:18 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Jan 2015 14:50:42 GMT",
"version": "v4"
}
] | 2015-04-06 | [
[
"Kay",
"Bernard S.",
"",
"York"
]
] | We point out that there are solutions to the scalar wave equation on 1+1 dimensional Minkowski space with finite energy tails which, if they reflect off a uniformly accelerated mirror due to (say) Dirichlet boundary conditions on it, develop an infinite stress-energy tensor on the mirror's Rindler horizon. We also show that, in the presence of an image mirror in the opposite Rindler wedge, suitable compactly supported arbitrarily small initial data on a suitable initial surface will develop an arbitrarily large stress-energy scalar near where the two horizons cross. Also, while there is a regular Hartle-Hawking-Israel-like state for the quantum theory between these two mirrors, there are coherent states built on it for which there are similar singularities in the expectation value of the renormalized stress-energy tensor. We conjecture that in other situations with analogous enclosed horizons such as a (maximally extended) Schwarzschild black hole in equilibrium in a (stationary spherical) box or the (maximally extended) Schwarzschild-AdS spacetime, there will be similar stress-energy singularities and almost-singularities -- leading to instability of the horizons when gravity is switched on and matter and gravity perturbations are allowed for. All this suggests it is incorrect to picture a black hole in equilibrium in a box or a Schwarzschild-AdS black hole as extending beyond the past and future horizons of a single Schwarzschild (/Schwarzschild-AdS) wedge. It would thus provide new evidence for 't Hooft's brick wall model while seeming to invalidate the picture in Maldacena's 'Eternal black holes in AdS'. It would thereby also support the validity of the author's matter-gravity entanglement hypothesis and of the paper 'Brick walls and AdS/CFT' by the author and Ort\'iz. |
gr-qc/0503118 | I.-Ching Yang | I-Ching Yang and Chia-Hsiu Tsai | The Evaluation of the M{\o}ller Energy Complex in Difference Coordinate
Representations | 8 pages | null | null | null | gr-qc | null | The M{\o}ller energy complex of Schwarzschild black hole solution in several
coodinates are evaluated. Our results show that the M{\o}ller energy complex is
independent of not only the purely spatial transformation, but also the shift
of time coordinate. So, we could conclude that a shift of time coordinates will
not change the energy which is obtained by using the definition of M{\o}ller
energy complex.
| [
{
"created": "Wed, 30 Mar 2005 14:17:12 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2005 10:56:10 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Yang",
"I-Ching",
""
],
[
"Tsai",
"Chia-Hsiu",
""
]
] | The M{\o}ller energy complex of Schwarzschild black hole solution in several coodinates are evaluated. Our results show that the M{\o}ller energy complex is independent of not only the purely spatial transformation, but also the shift of time coordinate. So, we could conclude that a shift of time coordinates will not change the energy which is obtained by using the definition of M{\o}ller energy complex. |
gr-qc/0512032 | Willians Barreto | L. Herrera, A. Di Prisco and W. Barreto | Thermo--inertial bouncing of a relativistic collapsing sphere: A
numerical model | 14 pages, 6 figures. To appear in Phys. Rev. D | Phys.Rev. D73 (2006) 024008 | 10.1103/PhysRevD.73.024008 | null | gr-qc astro-ph | null | We present a numerical model of a collapsing radiating sphere, whose boundary
surface undergoes bouncing due to a decreasing of its inertial mass density
(and, as expected from the equivalence principle, also of the ``gravitational''
force term) produced by the ``inertial'' term of the transport equation. This
model exhibits for the first time the consequences of such an effect, and shows
that under physically reasonable conditions this decreasing of the
gravitational term in the dynamic equation may be large enough as to revert the
collapse and produce a bouncing of the boundary surface of the sphere.
| [
{
"created": "Mon, 5 Dec 2005 22:09:19 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Barreto",
"W.",
""
]
] | We present a numerical model of a collapsing radiating sphere, whose boundary surface undergoes bouncing due to a decreasing of its inertial mass density (and, as expected from the equivalence principle, also of the ``gravitational'' force term) produced by the ``inertial'' term of the transport equation. This model exhibits for the first time the consequences of such an effect, and shows that under physically reasonable conditions this decreasing of the gravitational term in the dynamic equation may be large enough as to revert the collapse and produce a bouncing of the boundary surface of the sphere. |
gr-qc/9807040 | Kerstin Kunze | John D. Barrow, Kerstin E. Kunze | String Cosmology | 12 pages, Latex. Invited paper to appear in the special issue of the
Journal of Chaos, Solitons and Fractals on "Superstrings, M, F, S... Theory",
eds. C. Castro and M.S. El Naschie | Chaos Solitons Fractals 10:257,1999 | 10.1016/S0960-0779(98)00183-0 | SUSSEX-AST 98/7-1 | gr-qc astro-ph | null | An overview is given of the formulation of low-energy string cosmologies
together with examples of particular solutions, successes and problems of the
theory.
| [
{
"created": "Thu, 16 Jul 1998 12:01:51 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Barrow",
"John D.",
""
],
[
"Kunze",
"Kerstin E.",
""
]
] | An overview is given of the formulation of low-energy string cosmologies together with examples of particular solutions, successes and problems of the theory. |
gr-qc/0504045 | Sijie Gao | Sijie Gao and Jose' P. S. Lemos | The Tolman-Bondi--Vaidya Spacetime: matching timelike dust to null dust | 5 pages, no figure | Phys.Rev. D71 (2005) 084022 | 10.1103/PhysRevD.71.084022 | null | gr-qc | null | The Tolman-Bondi and Vaidya solutions are two solutions to Einstein equations
which describe dust particles and null fluid, respectively. We show that it is
possible to match the two solutions in one single spacetime, the
Tolman-Bondi--Vaidya spacetime. The new spacetime is divided by a null surface
with Tolman-Bondi dust on one side and Vaidya fluid on the other side. The
differentiability of the spacetime is discussed. By constructing a specific
solution, we show that the metric across the null surface can be at least $C^1$
and the stress-energy tensor is continuous.
| [
{
"created": "Mon, 11 Apr 2005 18:34:09 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gao",
"Sijie",
""
],
[
"Lemos",
"Jose' P. S.",
""
]
] | The Tolman-Bondi and Vaidya solutions are two solutions to Einstein equations which describe dust particles and null fluid, respectively. We show that it is possible to match the two solutions in one single spacetime, the Tolman-Bondi--Vaidya spacetime. The new spacetime is divided by a null surface with Tolman-Bondi dust on one side and Vaidya fluid on the other side. The differentiability of the spacetime is discussed. By constructing a specific solution, we show that the metric across the null surface can be at least $C^1$ and the stress-energy tensor is continuous. |
1207.5601 | David A. Craig | David A. Craig | Dynamical eigenfunctions and critical density in loop quantum cosmology | 23 pages, 8 figures. Minor corrections throughout. Significant
improvement to key figure illustrating behavior of the eigenfunctions.
Version to appear in Classical and Quantum Gravity | Class. Quantum Grav. 30 (2013) 035010 | 10.1088/0264-9381/30/3/035010 | PI-QG-250 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We offer a new, physically transparent argument for the existence of the
critical, universal maximum matter density in loop quantum cosmology for the
case of a flat Friedmann-Lemaitre-Robertson-Walker cosmology with scalar
matter. The argument is based on the existence of a sharp exponential
ultraviolet cutoff in momentum space on the eigenfunctions of the quantum
cosmological dynamical evolution operator (the gravitational part of the
Hamiltonian constraint), attributable to the fundamental discreteness of
spatial volume in loop quantum cosmology. The existence of the cutoff is proved
directly from recently found exact solutions for the eigenfunctions for this
model. As a consequence, the operators corresponding to the momentum of the
scalar field and the spatial volume approximately commute. The ultraviolet
cutoff then implies that the scalar momentum, though not a bounded operator, is
in effect bounded on subspaces of constant volume, leading to the upper bound
on the expectation value of the matter density. The maximum matter density is
universal (i.e. independent of the quantum state) because of the linear scaling
of the cutoff with volume. These heuristic arguments are supplemented by a new
proof in the volume representation of the existence of the maximum matter
density. The techniques employed to demonstrate the existence of the cutoff
also allow us to extract the large volume limit of the exact eigenfunctions,
confirming earlier numerical and analytical work showing that the
eigenfunctions approach superpositions of the eigenfunctions of the
Wheeler-DeWitt quantization of the same model. We argue that generic (not just
semiclassical) quantum states approach symmetric superpositions of expanding
and contracting universes.
| [
{
"created": "Tue, 24 Jul 2012 07:09:53 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Aug 2012 03:12:33 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Dec 2012 08:06:11 GMT",
"version": "v3"
}
] | 2013-01-23 | [
[
"Craig",
"David A.",
""
]
] | We offer a new, physically transparent argument for the existence of the critical, universal maximum matter density in loop quantum cosmology for the case of a flat Friedmann-Lemaitre-Robertson-Walker cosmology with scalar matter. The argument is based on the existence of a sharp exponential ultraviolet cutoff in momentum space on the eigenfunctions of the quantum cosmological dynamical evolution operator (the gravitational part of the Hamiltonian constraint), attributable to the fundamental discreteness of spatial volume in loop quantum cosmology. The existence of the cutoff is proved directly from recently found exact solutions for the eigenfunctions for this model. As a consequence, the operators corresponding to the momentum of the scalar field and the spatial volume approximately commute. The ultraviolet cutoff then implies that the scalar momentum, though not a bounded operator, is in effect bounded on subspaces of constant volume, leading to the upper bound on the expectation value of the matter density. The maximum matter density is universal (i.e. independent of the quantum state) because of the linear scaling of the cutoff with volume. These heuristic arguments are supplemented by a new proof in the volume representation of the existence of the maximum matter density. The techniques employed to demonstrate the existence of the cutoff also allow us to extract the large volume limit of the exact eigenfunctions, confirming earlier numerical and analytical work showing that the eigenfunctions approach superpositions of the eigenfunctions of the Wheeler-DeWitt quantization of the same model. We argue that generic (not just semiclassical) quantum states approach symmetric superpositions of expanding and contracting universes. |
1910.10580 | William Wolf | William J. Wolf and Macarena Lagos | Standard Sirens as a novel probe of dark energy | Updated to published version | Phys. Rev. Lett. 124, 061101 (2020) | 10.1103/PhysRevLett.124.061101 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological models with a dynamical dark energy field typically lead to a
modified propagation of gravitational waves via an effectively time-varying
gravitational coupling $G(t)$. The local variation of this coupling between the
time of emission and detection can be probed with standard sirens. Here we
discuss the role that Lunar Laser Ranging (LLR) and binary pulsar constraints
play in the prospects of constraining $G(t)$ with standard sirens. In
particular, we argue that LLR constrains the matter-matter gravitational
coupling $G_N(t)$, whereas binary pulsars and standard sirens constrain the
quadratic kinetic gravity self-interaction $G_{gw}(t)$. Generically, these two
couplings could be different in alternative cosmological models, in which case
LLR constraints are irrelevant for standard sirens. We use the Hulse-Taylor
pulsar data and show that observations are highly insensitive to time
variations of $G_{gw}(t)$ yet highly sensitive to $G_N(t)$. We thus conclude
that future gravitational waves data will become the best probe to test
$G_{gw}(t)$, and will hence provide novel constraints on dynamical dark energy
models.
| [
{
"created": "Wed, 23 Oct 2019 14:28:46 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Oct 2019 01:18:09 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Feb 2020 00:28:20 GMT",
"version": "v3"
}
] | 2020-02-19 | [
[
"Wolf",
"William J.",
""
],
[
"Lagos",
"Macarena",
""
]
] | Cosmological models with a dynamical dark energy field typically lead to a modified propagation of gravitational waves via an effectively time-varying gravitational coupling $G(t)$. The local variation of this coupling between the time of emission and detection can be probed with standard sirens. Here we discuss the role that Lunar Laser Ranging (LLR) and binary pulsar constraints play in the prospects of constraining $G(t)$ with standard sirens. In particular, we argue that LLR constrains the matter-matter gravitational coupling $G_N(t)$, whereas binary pulsars and standard sirens constrain the quadratic kinetic gravity self-interaction $G_{gw}(t)$. Generically, these two couplings could be different in alternative cosmological models, in which case LLR constraints are irrelevant for standard sirens. We use the Hulse-Taylor pulsar data and show that observations are highly insensitive to time variations of $G_{gw}(t)$ yet highly sensitive to $G_N(t)$. We thus conclude that future gravitational waves data will become the best probe to test $G_{gw}(t)$, and will hence provide novel constraints on dynamical dark energy models. |
1307.6232 | Yi Pan | Yi Pan, Alessandra Buonanno, Andrea Taracchini, Lawrence E. Kidder,
Abdul H. Mroue, Harald P. Pfeiffer, Mark A. Scheel, and Bela Szilagyi | Inspiral-merger-ringdown waveforms of spinning, precessing black-hole
binaries in the effective-one-body formalism | 17 pages, 10 figures | Phys. Rev. D 89, 084006 (2014) | 10.1103/PhysRevD.89.084006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a general procedure to generate spinning, precessing waveforms
that include inspiral, merger and ringdown stages in the effective-one-body
(EOB) approach. The procedure uses a precessing frame in which
precession-induced amplitude and phase modulations are minimized, and an
inertial frame, aligned with the spin of the final black hole, in which we
carry out the matching of the inspiral-plunge to merger-ringdown waveforms. As
a first application, we build spinning, precessing EOB waveforms for the
gravitational modes l=2 such that in the nonprecessing limit those waveforms
agree with the EOB waveforms recently calibrated to numerical-relativity
waveforms. Without recalibrating the EOB model, we then compare EOB and
post-Newtonian precessing waveforms to two numerical-relativity waveforms
produced by the Caltech-Cornell-CITA collaboration. The numerical waveforms are
strongly precessing and have 35 and 65 gravitational-wave cycles. We find a
remarkable agreement between EOB and numerical-relativity precessing waveforms
and spins' evolutions. The phase difference is ~ 0.2 rad at merger, while the
mismatches, computed using the advanced-LIGO noise spectral density, are below
2% when maximizing only on the time and phase at coalescence and on the
polarization angle.
| [
{
"created": "Tue, 23 Jul 2013 20:15:16 GMT",
"version": "v1"
}
] | 2014-04-23 | [
[
"Pan",
"Yi",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Taracchini",
"Andrea",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Mroue",
"Abdul H.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilagyi",
"Bela",
""
]
] | We describe a general procedure to generate spinning, precessing waveforms that include inspiral, merger and ringdown stages in the effective-one-body (EOB) approach. The procedure uses a precessing frame in which precession-induced amplitude and phase modulations are minimized, and an inertial frame, aligned with the spin of the final black hole, in which we carry out the matching of the inspiral-plunge to merger-ringdown waveforms. As a first application, we build spinning, precessing EOB waveforms for the gravitational modes l=2 such that in the nonprecessing limit those waveforms agree with the EOB waveforms recently calibrated to numerical-relativity waveforms. Without recalibrating the EOB model, we then compare EOB and post-Newtonian precessing waveforms to two numerical-relativity waveforms produced by the Caltech-Cornell-CITA collaboration. The numerical waveforms are strongly precessing and have 35 and 65 gravitational-wave cycles. We find a remarkable agreement between EOB and numerical-relativity precessing waveforms and spins' evolutions. The phase difference is ~ 0.2 rad at merger, while the mismatches, computed using the advanced-LIGO noise spectral density, are below 2% when maximizing only on the time and phase at coalescence and on the polarization angle. |
2205.15950 | Matt Visser | Sebastian Schuster (Charles University of Prague), Jessica Santiago
(Aristotle University of Thessaloniki), and Matt Visser (Victoria University
of Wellington) | ADM mass in warp drive spacetimes | V1:19 pages; V2: 22 pages. Authors re-ordered, abstract rewritten; 4
references added; improved presentation and discussion; calculations
unaltered; physics conclusions unaltered | null | 10.1007/s10714-022-03061-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | What happens when a warp bubble has mass? This seemingly innocent question
forces one to carefully formalize exactly what one means by a warp bubble,
exactly what one means by having the warp bubble "move" with respect to the
fixed stars, and forces one to more carefully examine the notion of mass in
warp-drive spacetimes. This is the goal of the present article. In this
process, we will see that often-made throw-away comments regarding "payloads"
are even simpler than commonly assumed, while there are two further, distinct
yet subtle ways in which a mass can appear in connection with a warp drive
space-time: One, that the warp bubble (not its payload) has the mass; two, that
the mass is a background feature in front of which the warp drive moves. For
simplicity, we consider generic Nat\'ario warp drives with zero-vorticity flow
field. The resulting spacetimes are sufficiently simple to allow an exact and
fully explicit computation of all of the stress-energy components, and verify
that (as expected) the null energy condition (NEC) is violated. Likewise the
weak, strong, and dominant energy conditions (WEC, SEC, DEC) are violated.
Indeed, this confirms the community's folk wisdom, and recent (fully general,
but implicit) results of the present authors which closed previous gaps in the
argument. However, folk wisdom should be carefully and critically examined
before being believed, and the present examples for general results will
greatly aid physical intuition.
| [
{
"created": "Tue, 31 May 2022 16:48:04 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Aug 2022 09:13:52 GMT",
"version": "v2"
}
] | 2023-01-18 | [
[
"Schuster",
"Sebastian",
"",
"Charles University of Prague"
],
[
"Santiago",
"Jessica",
"",
"Aristotle University of Thessaloniki"
],
[
"Visser",
"Matt",
"",
"Victoria University\n of Wellington"
]
] | What happens when a warp bubble has mass? This seemingly innocent question forces one to carefully formalize exactly what one means by a warp bubble, exactly what one means by having the warp bubble "move" with respect to the fixed stars, and forces one to more carefully examine the notion of mass in warp-drive spacetimes. This is the goal of the present article. In this process, we will see that often-made throw-away comments regarding "payloads" are even simpler than commonly assumed, while there are two further, distinct yet subtle ways in which a mass can appear in connection with a warp drive space-time: One, that the warp bubble (not its payload) has the mass; two, that the mass is a background feature in front of which the warp drive moves. For simplicity, we consider generic Nat\'ario warp drives with zero-vorticity flow field. The resulting spacetimes are sufficiently simple to allow an exact and fully explicit computation of all of the stress-energy components, and verify that (as expected) the null energy condition (NEC) is violated. Likewise the weak, strong, and dominant energy conditions (WEC, SEC, DEC) are violated. Indeed, this confirms the community's folk wisdom, and recent (fully general, but implicit) results of the present authors which closed previous gaps in the argument. However, folk wisdom should be carefully and critically examined before being believed, and the present examples for general results will greatly aid physical intuition. |
gr-qc/0702057 | Filipe Mena | Filipe C. Mena (Minho) and Paul Tod (Oxford) | Lanczos potentials and a definition of gravitational entropy for
perturbed FLRW space-times | 16 pages, submitted for publication in Classical and Quantum Gravity | Class.Quant.Grav.24:1733-1746,2007 | 10.1088/0264-9381/24/7/004 | null | gr-qc | null | We give a prescription for constructing a Lanczos potential for a
cosmological model which is a purely gravitational perturbation of a
Friedman-Lemaitre-Robertson-Walker space-time. For the radiation equation of
state, we find the Lanczos potential explicitly via Fourier transforms. As an
application, we follow up a suggestion of Penrose and propose a definition of
gravitational entropy for these cosmologies. With this definition, the
gravitational entropy initially is finite if and only if the initial Weyl
tensor is finite.
| [
{
"created": "Fri, 9 Feb 2007 20:44:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mena",
"Filipe C.",
"",
"Minho"
],
[
"Tod",
"Paul",
"",
"Oxford"
]
] | We give a prescription for constructing a Lanczos potential for a cosmological model which is a purely gravitational perturbation of a Friedman-Lemaitre-Robertson-Walker space-time. For the radiation equation of state, we find the Lanczos potential explicitly via Fourier transforms. As an application, we follow up a suggestion of Penrose and propose a definition of gravitational entropy for these cosmologies. With this definition, the gravitational entropy initially is finite if and only if the initial Weyl tensor is finite. |
1506.02145 | Gonzalo Olmo | Gonzalo J. Olmo, D. Rubiera-Garcia, and A. Sanchez-Puente | Geometric aspects of charged black holes in Palatini theories | 6 pages. Proceedings of the conference "Spanish Relativity Meeting -
ERE2014", held in Valencia (Spain) | J.Phys.Conf.Ser. 600 (2015) 1, 012042 | 10.1088/1742-6596/600/1/012042 | IFIC/15-55 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Charged black holes in gravity theories in the Palatini formalism present a
number of unique properties. Their innermost structure is topologically
nontrivial, representing a wormhole supported by a sourceless electric flux.
For certain values of their effective mass and charge curvature divergences may
be absent, and their event horizon may also disappear yielding a remnant. We
give an overview of the mathematical derivation of these solutions and discuss
their geodesic structure and other geometric properties.
| [
{
"created": "Sat, 6 Jun 2015 12:41:26 GMT",
"version": "v1"
}
] | 2015-07-31 | [
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"D.",
""
],
[
"Sanchez-Puente",
"A.",
""
]
] | Charged black holes in gravity theories in the Palatini formalism present a number of unique properties. Their innermost structure is topologically nontrivial, representing a wormhole supported by a sourceless electric flux. For certain values of their effective mass and charge curvature divergences may be absent, and their event horizon may also disappear yielding a remnant. We give an overview of the mathematical derivation of these solutions and discuss their geodesic structure and other geometric properties. |
2106.10303 | Zhu Yi | Zhu Yi and Zong-Hong Zhu | Inflationary attractors from a non-canonical kinetic term | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show explicitly how the T-model, E-model, and Hilltop inflations are
obtained from the inflation models with a non-canonical kinetic term and an
arbitrary potential. By this method, any attractor of observables $n_s$ and $r$
is possible. The presence of attractors poses a challenge to differentiate
inflation models.
| [
{
"created": "Fri, 18 Jun 2021 18:20:54 GMT",
"version": "v1"
}
] | 2021-06-22 | [
[
"Yi",
"Zhu",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | We show explicitly how the T-model, E-model, and Hilltop inflations are obtained from the inflation models with a non-canonical kinetic term and an arbitrary potential. By this method, any attractor of observables $n_s$ and $r$ is possible. The presence of attractors poses a challenge to differentiate inflation models. |
gr-qc/9312019 | Fonarev Oleg | Oleg A. Fonarev | Quantum Kinetic Equations and Cosmology | 10 pages | null | 10.1016/0375-9601(94)90361-1 | null | gr-qc astro-ph | null | We analyse quantum--kinetic effects in the early Universe. We show that
quantum corrections to the Vlasov equation give rise to a dynamical variation
of the gravitational constant. The value of the gravitational constant at the
Grand Unification epoch is shown to differ from its present value to about
$10^{-4} \div 10^{-3} \% $.
| [
{
"created": "Sat, 11 Dec 1993 12:38:52 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Fonarev",
"Oleg A.",
""
]
] | We analyse quantum--kinetic effects in the early Universe. We show that quantum corrections to the Vlasov equation give rise to a dynamical variation of the gravitational constant. The value of the gravitational constant at the Grand Unification epoch is shown to differ from its present value to about $10^{-4} \div 10^{-3} \% $. |
1504.05033 | Sergey Chervon | Aleksey Nikolaev and Sergey Chervon | Development of Zeldovich's approach for cosmological distances
measurement in the Friedmann Universe | 9 pages, 2 figures, comment is added | Eur. Phys. J. C (2015) 75:411 | 10.1140/epjc/s10052-015-3614-3 | LGCA 2015/4 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present our development of Zeldovich's ideas for the measurement of the
cosmological angular diameter distance (ADD) in the Friedmann Universe. We
derive the general differential equation for the ADD measurement which is valid
for an open, spatially-flat and closed universe, and for any stress energy
tensor. We solve the mentioned equations in terms of quadratures in a form
suitable for further numerical investigations for the present universe filled
by radiation, (baryonic and dark) matter and dark energy. We perform the
numerical investigation in the absence of radiation, and show the strong
dependence ADD on the filling of the cone of light rays (CLR). The difference
of the empty and totally filled CLR may reach 600-700 Mps. for the redshift
$f\simeq 3$.
| [
{
"created": "Mon, 20 Apr 2015 12:34:47 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Apr 2016 13:15:42 GMT",
"version": "v2"
}
] | 2016-04-08 | [
[
"Nikolaev",
"Aleksey",
""
],
[
"Chervon",
"Sergey",
""
]
] | We present our development of Zeldovich's ideas for the measurement of the cosmological angular diameter distance (ADD) in the Friedmann Universe. We derive the general differential equation for the ADD measurement which is valid for an open, spatially-flat and closed universe, and for any stress energy tensor. We solve the mentioned equations in terms of quadratures in a form suitable for further numerical investigations for the present universe filled by radiation, (baryonic and dark) matter and dark energy. We perform the numerical investigation in the absence of radiation, and show the strong dependence ADD on the filling of the cone of light rays (CLR). The difference of the empty and totally filled CLR may reach 600-700 Mps. for the redshift $f\simeq 3$. |
2103.03925 | Yiqi Xie | Yiqi Xie, Jun Zhang, Hector O. Silva, Claudia de Rham, Helvi Witek,
Nicolas Yunes | Square Peg in a Circular Hole: Choosing the Right Ansatz for Isolated
Black Holes in Generic Gravitational Theories | 7+5 pages, 1 figure, text and references updated, v2 matches version
published in PRL | Phys. Rev. Lett. 126, 241104 (2021) | 10.1103/PhysRevLett.126.241104 | Imperial/TP/2021/CdR/01 | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The metric of a spacetime can be greatly simplified if the spacetime is
circular. We prove that in generic effective theories of gravity, the spacetime
of a stationary, axisymmetric and asymptotically flat solution must be circular
if the solution can be obtained perturbatively from a solution in the general
relativity limit. This result applies to a broad class of gravitational
theories that include arbitrary scalars and vectors in their light sector, so
long as their nonstandard kinetic terms and nonmininal couplings to gravity are
treated perturbatively.
| [
{
"created": "Fri, 5 Mar 2021 20:17:40 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jun 2021 22:09:47 GMT",
"version": "v2"
}
] | 2021-06-22 | [
[
"Xie",
"Yiqi",
""
],
[
"Zhang",
"Jun",
""
],
[
"Silva",
"Hector O.",
""
],
[
"de Rham",
"Claudia",
""
],
[
"Witek",
"Helvi",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The metric of a spacetime can be greatly simplified if the spacetime is circular. We prove that in generic effective theories of gravity, the spacetime of a stationary, axisymmetric and asymptotically flat solution must be circular if the solution can be obtained perturbatively from a solution in the general relativity limit. This result applies to a broad class of gravitational theories that include arbitrary scalars and vectors in their light sector, so long as their nonstandard kinetic terms and nonmininal couplings to gravity are treated perturbatively. |
2303.02103 | Adri\'an Casado-Turri\'on | Adri\'an Casado-Turri\'on, \'Alvaro de la Cruz-Dombriz, Antonio Dobado | Physical non-viability of a wide class of $f(R)$ models and their
constant-curvature solutions | 20 pages, 1 table, no figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Constant-curvature solutions lie at the very core of gravitational physics,
with Schwarzschild and (Anti)-de Sitter being two of the most paradigmatic
examples. Although such kind of solutions are very well-known in General
Relativity, that is not the case for theories of gravity beyond the Einsteinian
paradigm. In this article, we provide a systematic overview on $f(R)$ models
allowing for constant-curvature solutions, as well as of the constant-curvature
solutions themselves. We conclude that the vast majority of these $f(R)$ models
suffer, in general, from several shortcomings rendering their viability
extremely limited, when not ruled out by physical evidence. Among these
deficiencies are instabilities (including previously unforeseen strong-coupling
problems) and issues limiting the predictive power of the models. Furthermore,
we will also show that most $f(R)$-exclusive constant-curvature solutions also
exhibit a variety of unphysical properties.
| [
{
"created": "Fri, 3 Mar 2023 17:40:20 GMT",
"version": "v1"
}
] | 2023-03-06 | [
[
"Casado-Turrión",
"Adrián",
""
],
[
"de la Cruz-Dombriz",
"Álvaro",
""
],
[
"Dobado",
"Antonio",
""
]
] | Constant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (Anti)-de Sitter being two of the most paradigmatic examples. Although such kind of solutions are very well-known in General Relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on $f(R)$ models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these $f(R)$ models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most $f(R)$-exclusive constant-curvature solutions also exhibit a variety of unphysical properties. |
1901.09098 | Valeriy I. Sbitnev | Valeriy I. Sbitnev | Quaternion algebra on 4D superfluid quantum space-time. Gravitomagnetism | 38 pages,15 figures. It will be printed in Foundations of Physics.
This matherial was reported on 4th International Conference on High Energy &
Particle Physics, Valencia, Spain | Foundations of Physics, 49(2), 107-143, 2019 | 10.1007/s10701-019-00236-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitomagnetic equations result from applying quaternionic differential
operators to the energy-momentum tensor. These equations are similar to the
Maxwell's EM equations. Both sets of the equations are isomorphic after
changing orientation of either the gravitomagnetic orbital force or the
magnetic induction. The gravitomagnetic equations turn out to be parent
equations generating the following set of equations: (a) the vorticity equation
giving solutions of vortices with nonzero vortex cores and with infinite
lifetime; (b) the Hamilton-Jacobi equation loaded by the quantum potential.
This equation in pair with the continuity equation leads to getting the
\Schrodinger equation describing a state of the superfluid quantum medium (a
modern version of the old ether); (c) gravitomagnetic wave equations loaded by
forces acting on the outer space. These waves obey to the Planck's law of
radiation.
| [
{
"created": "Mon, 21 Jan 2019 12:44:00 GMT",
"version": "v1"
}
] | 2019-02-21 | [
[
"Sbitnev",
"Valeriy I.",
""
]
] | Gravitomagnetic equations result from applying quaternionic differential operators to the energy-momentum tensor. These equations are similar to the Maxwell's EM equations. Both sets of the equations are isomorphic after changing orientation of either the gravitomagnetic orbital force or the magnetic induction. The gravitomagnetic equations turn out to be parent equations generating the following set of equations: (a) the vorticity equation giving solutions of vortices with nonzero vortex cores and with infinite lifetime; (b) the Hamilton-Jacobi equation loaded by the quantum potential. This equation in pair with the continuity equation leads to getting the \Schrodinger equation describing a state of the superfluid quantum medium (a modern version of the old ether); (c) gravitomagnetic wave equations loaded by forces acting on the outer space. These waves obey to the Planck's law of radiation. |
1104.4795 | P.A. Gonzalez | P.A. Gonz\'alez and Joel Saavedra | Comments on absorption cross section for Chern-Simons black holes in
five dimensions | 9 pages, 5 figures | null | 10.1142/S0217751X11054036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the effects of black hole mass on the absorption cross
section for a massive scalar field propagating in a 5-dimensional topological
Chern-Simons black hole at the low-frequency limit. We consider the two
branches of black hole solutions $(\alpha=\pm 1)$ and we show that, if the mass
of black hole increase the absorption cross section decreases at the
zero-frequency limit for the branch $\alpha=-1$ and for the other branch,
$\alpha=1$, the behavior is opposite, if the black hole mass increase the
absorption cross section increases. Also we find that beyond a certain
frequency value, the mass black hole does not affect the absorption cross
section.
| [
{
"created": "Mon, 25 Apr 2011 20:05:12 GMT",
"version": "v1"
},
{
"created": "Thu, 12 May 2011 13:11:12 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"González",
"P. A.",
""
],
[
"Saavedra",
"Joel",
""
]
] | In this paper we study the effects of black hole mass on the absorption cross section for a massive scalar field propagating in a 5-dimensional topological Chern-Simons black hole at the low-frequency limit. We consider the two branches of black hole solutions $(\alpha=\pm 1)$ and we show that, if the mass of black hole increase the absorption cross section decreases at the zero-frequency limit for the branch $\alpha=-1$ and for the other branch, $\alpha=1$, the behavior is opposite, if the black hole mass increase the absorption cross section increases. Also we find that beyond a certain frequency value, the mass black hole does not affect the absorption cross section. |
1502.00304 | Arman Taghavi-Chabert | Pawel Nurowski, Arman Taghavi-Chabert | A Goldberg-Sachs theorem in dimension three | 31 pages. v2: minor typographic changes in the bibliography | 2015 Class. Quantum Grav. 32 115009 | 10.1088/0264-9381/32/11/115009 | null | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a Goldberg-Sachs theorem in dimension three. To be precise, given a
three-dimensional Lorentzian manifold satisfying the topological massive
gravity equations, we provide necessary and sufficient conditions on the
tracefree Ricci tensor for the existence of a null line distribution whose
orthogonal complement is integrable and totally geodetic. This includes, in
particular, Kundt spacetimes that are solutions of the topological massive
gravity equations.
| [
{
"created": "Sun, 1 Feb 2015 20:24:02 GMT",
"version": "v1"
},
{
"created": "Wed, 13 May 2015 17:21:43 GMT",
"version": "v2"
}
] | 2015-05-14 | [
[
"Nurowski",
"Pawel",
""
],
[
"Taghavi-Chabert",
"Arman",
""
]
] | We prove a Goldberg-Sachs theorem in dimension three. To be precise, given a three-dimensional Lorentzian manifold satisfying the topological massive gravity equations, we provide necessary and sufficient conditions on the tracefree Ricci tensor for the existence of a null line distribution whose orthogonal complement is integrable and totally geodetic. This includes, in particular, Kundt spacetimes that are solutions of the topological massive gravity equations. |
2205.10863 | Sobhan Kazempour | Sobhan Kazempour, Amin Rezaei Akbarieh, Hossein Motavalli and Lijing
Shao | Cosmology of Dirac-Born-Infeld dRGT massive gravity | arXiv admin note: text overlap with arXiv:2204.05595 | Phys. Rev. D 106, 023508 (2022) | 10.1103/PhysRevD.106.023508 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We introduce the cosmological analysis of the Dirac-Born-Infeld dRGT massive
gravity theory which is a new extension of de Rham-Gabadadze-Tolley (dRGT)
massive gravity. In this theory, we consider the Dirac-Born-Infeld (DBI) scalar
field which is coupled to the graviton field. Moreover, we perform the
cosmological background equations, and we demonstrate the self-accelerating
background solutions. We show that the theory consists of self-accelerating
solutions with an effective cosmological constant. In the following, we exhibit
tensor perturbations analyses and achieve the dispersion relation of
gravitational waves. We analyze the propagation of gravitational perturbation
in the Friedmann-Lema\^itre-Robertson-Walker cosmology in the DBI dRGT massive
gravity. Finally, we present the vector and scalar perturbations to show the
stability conditions of the theory.
| [
{
"created": "Sun, 22 May 2022 16:31:59 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2022 08:16:30 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jul 2022 15:03:41 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Jul 2022 08:08:08 GMT",
"version": "v4"
}
] | 2022-07-18 | [
[
"Kazempour",
"Sobhan",
""
],
[
"Akbarieh",
"Amin Rezaei",
""
],
[
"Motavalli",
"Hossein",
""
],
[
"Shao",
"Lijing",
""
]
] | We introduce the cosmological analysis of the Dirac-Born-Infeld dRGT massive gravity theory which is a new extension of de Rham-Gabadadze-Tolley (dRGT) massive gravity. In this theory, we consider the Dirac-Born-Infeld (DBI) scalar field which is coupled to the graviton field. Moreover, we perform the cosmological background equations, and we demonstrate the self-accelerating background solutions. We show that the theory consists of self-accelerating solutions with an effective cosmological constant. In the following, we exhibit tensor perturbations analyses and achieve the dispersion relation of gravitational waves. We analyze the propagation of gravitational perturbation in the Friedmann-Lema\^itre-Robertson-Walker cosmology in the DBI dRGT massive gravity. Finally, we present the vector and scalar perturbations to show the stability conditions of the theory. |
1809.05305 | Andrea Geralico | Donato Bini, Andrea Geralico | On the energy content of electromagnetic and gravitational plane waves
through super-energy tensors | 22 pages, 3 figures, iop macros used. Slightly modified version with
respect to the published one: revised quotation of references, new Appendix A
included, typos corrected | Class. Quantum Grav. 35, 165006 (2018) | 10.1088/1361-6382/aad0b0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The energy content of (exact) electromagnetic and gravitational plane waves
is studied in terms of super-energy tensors (the Bel, Bel-Robinson and the
--less familiar-- Chevreton tensors) and natural observers. Starting from the
case of single waves, the more interesting situation of colliding waves is then
discussed, where the nonlinearities of the Einstein's theory play an important
role. The causality properties of the super-momentum four vectors associated
with each of these tensors are also investigated when passing from the
single-wave regions to the interaction region.
| [
{
"created": "Fri, 14 Sep 2018 08:54:23 GMT",
"version": "v1"
}
] | 2018-09-17 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The energy content of (exact) electromagnetic and gravitational plane waves is studied in terms of super-energy tensors (the Bel, Bel-Robinson and the --less familiar-- Chevreton tensors) and natural observers. Starting from the case of single waves, the more interesting situation of colliding waves is then discussed, where the nonlinearities of the Einstein's theory play an important role. The causality properties of the super-momentum four vectors associated with each of these tensors are also investigated when passing from the single-wave regions to the interaction region. |
2304.02949 | Avik De Dr. | Hamid Shabani, Avik De, and Tee-How Loo | Phase-space analysis of a novel cosmological model in $f(Q)$ theory | Accepted for publication in EPJC | null | 10.1140/epjc/s10052-023-11722-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The vanishing affine connections have been used solely while adopting the
modified $f(Q)$ gravity theory to the cosmology. Consequently, researchers
could not get beyond what is already known in $f(T)$ theory earlier. To
alleviate this problem, in the present manuscript we investigate a recently
proposed construction of $f(Q)$ theory using non-vanishing affine connection in
the spatially flat FLRW spacetime. We then investigate the cosmological
solutions of $f(Q)$ theory for a perfect fluid through the phase space
analysis. We introduce few variables and dimensionless parameters to construct
the corresponding equations suitable for the dynamical system approach. The
conservation of the energy-momentum tensor leads to a constraint equation that
relates the dynamical variables. Briefly, both unstable and stable de Sitter
solutions appear which correspond to early and late times accelerated
expansions. Also, unstable points corresponding to the matter dominated and
radiation dominated eras have been found which do exist for every $f(Q)$
function. As a result, the present discussion shows that $f(Q)$ gravity endowed
by non-vanishing affine connections is capable of explaining a true sequence of
cosmic eras.
| [
{
"created": "Thu, 6 Apr 2023 09:19:45 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2023 06:00:38 GMT",
"version": "v2"
}
] | 2023-07-12 | [
[
"Shabani",
"Hamid",
""
],
[
"De",
"Avik",
""
],
[
"Loo",
"Tee-How",
""
]
] | The vanishing affine connections have been used solely while adopting the modified $f(Q)$ gravity theory to the cosmology. Consequently, researchers could not get beyond what is already known in $f(T)$ theory earlier. To alleviate this problem, in the present manuscript we investigate a recently proposed construction of $f(Q)$ theory using non-vanishing affine connection in the spatially flat FLRW spacetime. We then investigate the cosmological solutions of $f(Q)$ theory for a perfect fluid through the phase space analysis. We introduce few variables and dimensionless parameters to construct the corresponding equations suitable for the dynamical system approach. The conservation of the energy-momentum tensor leads to a constraint equation that relates the dynamical variables. Briefly, both unstable and stable de Sitter solutions appear which correspond to early and late times accelerated expansions. Also, unstable points corresponding to the matter dominated and radiation dominated eras have been found which do exist for every $f(Q)$ function. As a result, the present discussion shows that $f(Q)$ gravity endowed by non-vanishing affine connections is capable of explaining a true sequence of cosmic eras. |
2206.14158 | Orlando Luongo | Alessio Belfiglio, Roberto Giamb\`o, Orlando Luongo | Alleviating the cosmological constant problem from particle production | 23 pages; 7 figures; 2 tables | Class.Quant.Grav. 40 (2023) 10, 105004 | 10.1088/1361-6382/accc00 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore a toy model mechanism of geometric cancellation, alleviating the
(classical) cosmological constant problem. To do so, we assume at primordial
times that vacuum energy fuels an inflationary quadratic hilltop potential
nonminimally coupled to gravity through a standard Yukawa-like interacting
term, whose background lies on a perturbed Friedmann-Robertson-Walker metric.
We demonstrate how vacuum energy release transforms into geometric particles,
adopting a quasi-de Sitter phase where we compute the expected particle density
and mass ranges. Perturbations are introduced by means of the usual
external-field appproximation, so that the back-reaction of the created
particles on the geometry is not considered here. We discuss the limitations of
this approach and we also suggest possible refinements. We then propose the
most suitable dark matter candidates, showing under which circumstances we can
interpret dark matter as constituted by geometric quasiparticles. We confront
our predictions with quantum particle production and constraints made using a
Higgs portal. In addition, the role of the bare cosmological constant is
reinterpreted to speed up the universe today. Thus, consequences on the
standard $\Lambda$CDM paradigm are critically highlighted, showing how both
coincidence and fine-tuning issues can be healed requiring the Israel-Darmois
matching conditions between our involved inhomogeneous and homogeneous phases.
| [
{
"created": "Tue, 28 Jun 2022 17:06:26 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jun 2024 12:18:20 GMT",
"version": "v2"
}
] | 2024-06-12 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Giambò",
"Roberto",
""
],
[
"Luongo",
"Orlando",
""
]
] | We explore a toy model mechanism of geometric cancellation, alleviating the (classical) cosmological constant problem. To do so, we assume at primordial times that vacuum energy fuels an inflationary quadratic hilltop potential nonminimally coupled to gravity through a standard Yukawa-like interacting term, whose background lies on a perturbed Friedmann-Robertson-Walker metric. We demonstrate how vacuum energy release transforms into geometric particles, adopting a quasi-de Sitter phase where we compute the expected particle density and mass ranges. Perturbations are introduced by means of the usual external-field appproximation, so that the back-reaction of the created particles on the geometry is not considered here. We discuss the limitations of this approach and we also suggest possible refinements. We then propose the most suitable dark matter candidates, showing under which circumstances we can interpret dark matter as constituted by geometric quasiparticles. We confront our predictions with quantum particle production and constraints made using a Higgs portal. In addition, the role of the bare cosmological constant is reinterpreted to speed up the universe today. Thus, consequences on the standard $\Lambda$CDM paradigm are critically highlighted, showing how both coincidence and fine-tuning issues can be healed requiring the Israel-Darmois matching conditions between our involved inhomogeneous and homogeneous phases. |
2111.07219 | Javier M. Antelis | Javier M. Antelis, Marco Cavaglia, Travis Hansen, Manuel D. Morales,
Claudia Moreno, Soma Mukherjee, Marek J. Szczepa\'nczyk, Michele Zanolin | Using supervised learning algorithms as a follow-up method in the search
of gravitational waves from core-collapse supernovae | null | null | 10.1103/PhysRevD.105.084054 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a follow-up method based on supervised machine learning (ML) to
improve the performance in the search of gravitational wave (GW) burts from
core-collapse supernovae (CCSNe) using the coherent WaveBurst (cWB) pipeline.
The ML model discriminates noise from signal events using as features a set of
reconstruction parameters provided by cWB. Detected noise events are discarded
yielding to a reduction of the false alarm rate (FAR) and of the false alarm
probability (FAP) thus enhancing of the statistical significance. We tested the
proposed method using strain data from the first half of the third observing
run of advanced LIGO, and CCSNe GW signals extracted from 3D simulations. The
ML model is learned using a dataset of noise and signal events, and then it is
used to identify and discard noise events in cWB analyses. Noise and signal
reduction levels were examined in single detector networks (L1 and H1) and two
detector network (L1H1). The FAR was reduced by a factor of $\sim10$ to
$\sim100$, there was an enhancement in the statistical significance of $\sim1$
to $\sim2\sigma$, while there was no impact in detection efficiencies.
| [
{
"created": "Sun, 14 Nov 2021 01:31:11 GMT",
"version": "v1"
}
] | 2022-05-11 | [
[
"Antelis",
"Javier M.",
""
],
[
"Cavaglia",
"Marco",
""
],
[
"Hansen",
"Travis",
""
],
[
"Morales",
"Manuel D.",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Mukherjee",
"Soma",
""
],
[
"Szczepańczyk",
"Marek J.",
""
],
[
"Zanolin",
"Michele",
""
]
] | We present a follow-up method based on supervised machine learning (ML) to improve the performance in the search of gravitational wave (GW) burts from core-collapse supernovae (CCSNe) using the coherent WaveBurst (cWB) pipeline. The ML model discriminates noise from signal events using as features a set of reconstruction parameters provided by cWB. Detected noise events are discarded yielding to a reduction of the false alarm rate (FAR) and of the false alarm probability (FAP) thus enhancing of the statistical significance. We tested the proposed method using strain data from the first half of the third observing run of advanced LIGO, and CCSNe GW signals extracted from 3D simulations. The ML model is learned using a dataset of noise and signal events, and then it is used to identify and discard noise events in cWB analyses. Noise and signal reduction levels were examined in single detector networks (L1 and H1) and two detector network (L1H1). The FAR was reduced by a factor of $\sim10$ to $\sim100$, there was an enhancement in the statistical significance of $\sim1$ to $\sim2\sigma$, while there was no impact in detection efficiencies. |
gr-qc/0406117 | Emanuel Gallo | Emanuel Gallo | Two-dimensional Riemannian and Lorentzian geometries from second order
ODEs | 9 pages, final version to appear in J. Math. Phys | J.Math.Phys. 45 (2004) 4186-4190 | 10.1063/1.1806261 | null | gr-qc | null | In this note we give an alternative geometrical derivation of the results
recently presented by Garcia-Godinez, Newman and Silva-Ortigoza in [1] on the
class of all two-dimensional riemannian and lorentzian metrics from 2nd order
ODEs which are in duality with the two dimensional Hamilton-Jacobi equation. We
show that, as it happens in the Null Surface Formulation of General Relativity,
the Wuschmann-like condition can be obtained as a requirement of a vanishing
torsion tensor. Furthermore, from these second order ODEs we obtain the
associated Cartan connections.
| [
{
"created": "Tue, 29 Jun 2004 20:45:04 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jul 2004 15:57:11 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Aug 2004 21:52:47 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Gallo",
"Emanuel",
""
]
] | In this note we give an alternative geometrical derivation of the results recently presented by Garcia-Godinez, Newman and Silva-Ortigoza in [1] on the class of all two-dimensional riemannian and lorentzian metrics from 2nd order ODEs which are in duality with the two dimensional Hamilton-Jacobi equation. We show that, as it happens in the Null Surface Formulation of General Relativity, the Wuschmann-like condition can be obtained as a requirement of a vanishing torsion tensor. Furthermore, from these second order ODEs we obtain the associated Cartan connections. |
2402.01192 | Debojit Paul ` | Debojit Paul, Pranjali Bhattacharjee, Sanjeev Kalita | Kerr-scalaron metric and astronomical consequences near the Galactic
Center black hole | 22 pages, 14 figures, Accepted for publication in ApJ | ApJ 964 127 (2024) | 10.3847/1538-4357/ad24f0 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astronomical tests of spacetime metric and gravitation theory near the
Galactic Center (GC) black hole, Sgr A* have gained momentum with the
observations of compact stellar orbits near the black hole and measurement of
the black hole shadow. Deviation from the Kerr metric is a potential signature
of modified gravity theory. In this work, we use Newman-Janis algorithm to
construct an axially symmetric and asymptotically flat metric in f(R) scalaron
gravity theory. We call it as Kerr-scalaron metric. For studying astronomical
consequences of the new metric we use the compact stellar orbits and the black
hole shadow. We use the observed size of the emission ring of the GC black hole
shadow for estimating deviation of the new metric from general relativity. It
has been found that scalarons with mass within $10^{-17}$ eV - $10^{-16}$ eV
are compatible with the observed emission ring size for black hole spin
$\chi=0.9$. Schwarzschild limit of the pericenter shift is estimated for
compact stellar orbits near the black hole. General relativistic pericenter
shift in wider orbits including S-stars such as S4716 and S2 has been
reproduced with these scalarons. The parameter $f_{SP}$ measuring deviation
from Schwarzschild pericenter shift has been found as $f_{SP}=1.00-1.04$ within
stellar orbits having semi-major axes $45$ au - $100$ au. Scalarons have the
capability to dominate Schwarzschild precession for orbits much below $45$ au.
Lense-Thirring (LT) precession with the new metric is estimated for the compact
orbits. The massive scalarons produce LT precession with magnitude
($12.25-24.5$) $\mu$as/yr in the orbit of S2. The LT precession time scale is
within $0.1$% of the age of the S-stars.
| [
{
"created": "Fri, 2 Feb 2024 07:29:28 GMT",
"version": "v1"
}
] | 2024-04-10 | [
[
"Paul",
"Debojit",
""
],
[
"Bhattacharjee",
"Pranjali",
""
],
[
"Kalita",
"Sanjeev",
""
]
] | Astronomical tests of spacetime metric and gravitation theory near the Galactic Center (GC) black hole, Sgr A* have gained momentum with the observations of compact stellar orbits near the black hole and measurement of the black hole shadow. Deviation from the Kerr metric is a potential signature of modified gravity theory. In this work, we use Newman-Janis algorithm to construct an axially symmetric and asymptotically flat metric in f(R) scalaron gravity theory. We call it as Kerr-scalaron metric. For studying astronomical consequences of the new metric we use the compact stellar orbits and the black hole shadow. We use the observed size of the emission ring of the GC black hole shadow for estimating deviation of the new metric from general relativity. It has been found that scalarons with mass within $10^{-17}$ eV - $10^{-16}$ eV are compatible with the observed emission ring size for black hole spin $\chi=0.9$. Schwarzschild limit of the pericenter shift is estimated for compact stellar orbits near the black hole. General relativistic pericenter shift in wider orbits including S-stars such as S4716 and S2 has been reproduced with these scalarons. The parameter $f_{SP}$ measuring deviation from Schwarzschild pericenter shift has been found as $f_{SP}=1.00-1.04$ within stellar orbits having semi-major axes $45$ au - $100$ au. Scalarons have the capability to dominate Schwarzschild precession for orbits much below $45$ au. Lense-Thirring (LT) precession with the new metric is estimated for the compact orbits. The massive scalarons produce LT precession with magnitude ($12.25-24.5$) $\mu$as/yr in the orbit of S2. The LT precession time scale is within $0.1$% of the age of the S-stars. |
2401.02003 | Xinliang An | Xinliang An | Naked Singularity Censoring with Anisotropic Apparent Horizon | 90 pages, announced in December 2022 | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://creativecommons.org/licenses/by/4.0/ | Employing the Einstein-scalar field system, we demonstrate an approach for
proving high co-dimensional nonlinear instability of naked-singularity
solutions as constructed by Christodoulou in [18]. We further investigate the
censorship of Christodoulou's naked singularity and show that a tiny
anisotropic perturbation arising from the outgoing characteristic initial data
would lead to the emergence of an anisotropic apparent horizon, which covers
and censors the naked singularity. Our approach advances the hyperbolic
short-pulse method by not requiring the aid of additional large parameters, by
permitting the use of initial perturbations for the shear tensor and the
derivative of scalar field to be with finite $BV$ and $C^0$ norms, and by
allowing the initial perturbation to be arbitrarily small in scale-critical
norms. New elliptic arguments based on non-perturbative methods are also
developed.
| [
{
"created": "Wed, 3 Jan 2024 23:50:30 GMT",
"version": "v1"
}
] | 2024-01-05 | [
[
"An",
"Xinliang",
""
]
] | Employing the Einstein-scalar field system, we demonstrate an approach for proving high co-dimensional nonlinear instability of naked-singularity solutions as constructed by Christodoulou in [18]. We further investigate the censorship of Christodoulou's naked singularity and show that a tiny anisotropic perturbation arising from the outgoing characteristic initial data would lead to the emergence of an anisotropic apparent horizon, which covers and censors the naked singularity. Our approach advances the hyperbolic short-pulse method by not requiring the aid of additional large parameters, by permitting the use of initial perturbations for the shear tensor and the derivative of scalar field to be with finite $BV$ and $C^0$ norms, and by allowing the initial perturbation to be arbitrarily small in scale-critical norms. New elliptic arguments based on non-perturbative methods are also developed. |
1807.10381 | Karthik Shankar | Karthik H. Shankar | Eternally oscillating zero energy Universe | View the published article at https://rdcu.be/b2zkW | Gen Relativ Gravit 52, 23 (2020) | 10.1007/s10714-020-02671-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question of whether the universe is eternal or if it had a singular
moment of creation is deeply intriguing. Although different versions of steady
state and oscillatory models of eternal universe have been envisaged, empirical
evidence suggests a singular moment of creation at the big bang. Here we
analyze the oscillatory solutions for the universe in a modified theory of
gravity THED (Torsion Hides Extra-Dimension) and evaluate them by fitting Type
1a supernovae redshift data. THED-gravity exactly mimics General Relativity at
the kinematical level, while the modifications in its dynamical equations allow
the universe to bounce between a minimum size and a maximum size with a zero
average energy within each oscillation. The optimally fit oscillatory solutions
correspond to a universe with (i) a small matter density requiring little to no
dark matter, (ii) a significantly negative spatial curvature, (iii) a tiny
negative dark energy. Alternatively, there exists non-oscillating solutions
that appear as an ever-expanding universe from a single bounce preceded by a
collapse from the infinite past. These ever-expanding solutions provide
marginally better fits to the supernova redshift data, but require larger
matter densities and positive dark energy along with a positive spatial
curvature. A qualitative analysis of CMB power spectrum in the modified theory
suggests a significant negative spatial curvature, which is in stark contrast
to a near-zero curvature in the standard big bang theory. An independent
constraint on the spatial curvature can further shed light on discriminating
the ever expanding and oscillatory universe scenarios.
| [
{
"created": "Thu, 26 Jul 2018 22:02:50 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2019 19:42:10 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Mar 2020 00:32:46 GMT",
"version": "v3"
}
] | 2020-03-09 | [
[
"Shankar",
"Karthik H.",
""
]
] | The question of whether the universe is eternal or if it had a singular moment of creation is deeply intriguing. Although different versions of steady state and oscillatory models of eternal universe have been envisaged, empirical evidence suggests a singular moment of creation at the big bang. Here we analyze the oscillatory solutions for the universe in a modified theory of gravity THED (Torsion Hides Extra-Dimension) and evaluate them by fitting Type 1a supernovae redshift data. THED-gravity exactly mimics General Relativity at the kinematical level, while the modifications in its dynamical equations allow the universe to bounce between a minimum size and a maximum size with a zero average energy within each oscillation. The optimally fit oscillatory solutions correspond to a universe with (i) a small matter density requiring little to no dark matter, (ii) a significantly negative spatial curvature, (iii) a tiny negative dark energy. Alternatively, there exists non-oscillating solutions that appear as an ever-expanding universe from a single bounce preceded by a collapse from the infinite past. These ever-expanding solutions provide marginally better fits to the supernova redshift data, but require larger matter densities and positive dark energy along with a positive spatial curvature. A qualitative analysis of CMB power spectrum in the modified theory suggests a significant negative spatial curvature, which is in stark contrast to a near-zero curvature in the standard big bang theory. An independent constraint on the spatial curvature can further shed light on discriminating the ever expanding and oscillatory universe scenarios. |
2105.07053 | Juan Margalef-Bentabol | Fernando Barbero G., Juan Margalef-Bentabol, Valle Varo, Eduardo J.S.
Villase\~nor | Palatini gravity with nonmetricity, torsion, and boundaries in metric
and connection variables | null | Physical Review D, 104 (2021) 044046 | 10.1103/PhysRevD.104.044046 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by-sa/4.0/ | We prove the equivalence in the covariant phase space of the metric and
connection formulations for Palatini gravity, with nonmetricity and torsion, on
a spacetime manifold with boundary. To this end, we will rely on the
cohomological approach provided by the relative bicomplex framework. Finally,
we discuss some of the physical implications derived from this equivalence in
the context of singularity identification through curvature invariants.
| [
{
"created": "Fri, 14 May 2021 19:53:10 GMT",
"version": "v1"
}
] | 2021-09-28 | [
[
"G.",
"Fernando Barbero",
""
],
[
"Margalef-Bentabol",
"Juan",
""
],
[
"Varo",
"Valle",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We prove the equivalence in the covariant phase space of the metric and connection formulations for Palatini gravity, with nonmetricity and torsion, on a spacetime manifold with boundary. To this end, we will rely on the cohomological approach provided by the relative bicomplex framework. Finally, we discuss some of the physical implications derived from this equivalence in the context of singularity identification through curvature invariants. |
gr-qc/9608032 | Carlo Rovelli | Carlo Rovelli | Loop Quantum Gravity and Black Hole Physics | Lecture at the Journees Relativistes, Ascona 1996. LaTeX, 1
PostScript figure (a.eps), uses epsfig.sty | Helv.Phys.Acta 69:582-611,1996 | null | null | gr-qc hep-th | null | I summarize the basic ideas and formalism of loop quantum gravity. I
illustrate the results on the discrete aspects of quantum geometry and two
applications of these results to black hole physics. In particular, I discuss
in detail a derivation of the Bekenstein-Hawking formula for the entropy of a
black hole from first principles.
| [
{
"created": "Wed, 14 Aug 1996 16:59:18 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Rovelli",
"Carlo",
""
]
] | I summarize the basic ideas and formalism of loop quantum gravity. I illustrate the results on the discrete aspects of quantum geometry and two applications of these results to black hole physics. In particular, I discuss in detail a derivation of the Bekenstein-Hawking formula for the entropy of a black hole from first principles. |
2005.11850 | Yiwen Huang | Yiwen Huang, Carl-Johan Haster, Salvatore Vitale, Vijay Varma,
Francois Foucart, Sylvia Biscoveanu | Statistical and systematic uncertainties in extracting the source
properties of neutron star - black hole binaries with gravitational waves | 39 pages, 24 figures, 15 tables | Phys. Rev. D 103, 083001 (2021) | 10.1103/PhysRevD.103.083001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted by neutron star black hole mergers encode key
properties of neutron stars - such as their size, maximum mass and spins - and
black holes. However, the presence of matter and the high mass ratio makes
generating long and accurate waveforms from these systems hard to do with
numerical relativity, and not much is known about systematic uncertainties due
to waveform modeling. We simulate gravitational waves from neutron star black
hole mergers by hybridizing numerical relativity waveforms produced with the
SpEC code with a recent numerical relativity surrogate NRHybSur3dq8Tidal. These
signals are analyzed using a range of available waveform families, and
statistical and systematic errors are reported. We find that at a network
signal-to-noise ratio (SNR) of 30, statistical uncertainties are usually larger
than systematic offsets, while at an SNR of 70 the two become comparable. The
individual black hole and neutron star masses, as well as the mass ratios, are
typically measured very precisely, though not always accurately at high SNR. At
a SNR of 30 the neutron star tidal deformability can only be bound from above,
while for louder sources it can be measured and constrained away from zero. All
neutron stars in our simulations are non-spinning, but in no case we can
constrain the neutron star spin to be smaller than $\sim0.4$ (90% credible
interval). Waveform families whose late inspiral has been tuned specifically
for neutron star black hole signals typically yield the most accurate
characterization of the source parameters. Their measurements are in tension
with those obtained using waveform families tuned against binary neutron stars,
even for mass ratios that could be relevant for both binary neutron stars and
neutron star black holes mergers.
| [
{
"created": "Sun, 24 May 2020 22:16:37 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Aug 2020 05:18:30 GMT",
"version": "v2"
}
] | 2021-04-14 | [
[
"Huang",
"Yiwen",
""
],
[
"Haster",
"Carl-Johan",
""
],
[
"Vitale",
"Salvatore",
""
],
[
"Varma",
"Vijay",
""
],
[
"Foucart",
"Francois",
""
],
[
"Biscoveanu",
"Sylvia",
""
]
] | Gravitational waves emitted by neutron star black hole mergers encode key properties of neutron stars - such as their size, maximum mass and spins - and black holes. However, the presence of matter and the high mass ratio makes generating long and accurate waveforms from these systems hard to do with numerical relativity, and not much is known about systematic uncertainties due to waveform modeling. We simulate gravitational waves from neutron star black hole mergers by hybridizing numerical relativity waveforms produced with the SpEC code with a recent numerical relativity surrogate NRHybSur3dq8Tidal. These signals are analyzed using a range of available waveform families, and statistical and systematic errors are reported. We find that at a network signal-to-noise ratio (SNR) of 30, statistical uncertainties are usually larger than systematic offsets, while at an SNR of 70 the two become comparable. The individual black hole and neutron star masses, as well as the mass ratios, are typically measured very precisely, though not always accurately at high SNR. At a SNR of 30 the neutron star tidal deformability can only be bound from above, while for louder sources it can be measured and constrained away from zero. All neutron stars in our simulations are non-spinning, but in no case we can constrain the neutron star spin to be smaller than $\sim0.4$ (90% credible interval). Waveform families whose late inspiral has been tuned specifically for neutron star black hole signals typically yield the most accurate characterization of the source parameters. Their measurements are in tension with those obtained using waveform families tuned against binary neutron stars, even for mass ratios that could be relevant for both binary neutron stars and neutron star black holes mergers. |
gr-qc/0603021 | Andrew Beckwith | A.W.Beckwith | How can Brane World physics influence Axion temperature dependence,
initial vacuum states, and permissible solutions to the Wheeler-De Witt
equation? | 36 pages, 1 figure. In foot note and general font style which will be
adhered to by the electronic journal of theoretical physics, once this paper
is published by them | Electron.J.Theor.Phys.4N15:105-142,2007 | null | null | gr-qc | null | We are investigating if the Jeans instability criteria mandading a low
entropy,low temperature initial pre inflation state configuration can be
recociled with thermal conditions of temperature at or above ten to the 12
power Kelvin, or higher,when cosmic inflation physics takes over. We justify
this by pointing to the Akshenkar, Pawlowski, and Singh (2006) article about a
prior universe being modeled via their quantum bounce which states that this
prior universe geometrically can be modeled via a discretized Wheeler - De Witt
equation. This allows a way of getting around the fact that conventional
cosmological CMB is limited by a barrier as of a red shift limit of about z =
1000,as to photons, and to come up with a working model of quintessence scalar
fields which permits relic generation of dark matter/dark energy as well as
relic gravitons.
| [
{
"created": "Wed, 8 Mar 2006 04:48:10 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jul 2006 16:19:38 GMT",
"version": "v10"
},
{
"created": "Mon, 3 Jul 2006 23:16:14 GMT",
"version": "v11"
},
{
"created": "Sat, 29 Jul 2006 06:22:46 GMT",
"version": "v12"
},
{
"created": "Wed, 27 Sep 2006 21:51:23 GMT",
"version": "v13"
},
{
"created": "Thu, 19 Oct 2006 18:21:14 GMT",
"version": "v14"
},
{
"created": "Thu, 16 Nov 2006 20:48:00 GMT",
"version": "v15"
},
{
"created": "Tue, 9 Jan 2007 20:34:17 GMT",
"version": "v16"
},
{
"created": "Wed, 11 Apr 2007 14:47:48 GMT",
"version": "v17"
},
{
"created": "Fri, 17 Mar 2006 18:06:02 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Mar 2006 16:56:37 GMT",
"version": "v3"
},
{
"created": "Fri, 7 Apr 2006 20:35:27 GMT",
"version": "v4"
},
{
"created": "Tue, 11 Apr 2006 17:17:24 GMT",
"version": "v5"
},
{
"created": "Tue, 18 Apr 2006 19:30:59 GMT",
"version": "v6"
},
{
"created": "Tue, 18 Apr 2006 20:14:11 GMT",
"version": "v7"
},
{
"created": "Tue, 9 May 2006 21:44:09 GMT",
"version": "v8"
},
{
"created": "Thu, 11 May 2006 22:07:26 GMT",
"version": "v9"
}
] | 2008-11-26 | [
[
"Beckwith",
"A. W.",
""
]
] | We are investigating if the Jeans instability criteria mandading a low entropy,low temperature initial pre inflation state configuration can be recociled with thermal conditions of temperature at or above ten to the 12 power Kelvin, or higher,when cosmic inflation physics takes over. We justify this by pointing to the Akshenkar, Pawlowski, and Singh (2006) article about a prior universe being modeled via their quantum bounce which states that this prior universe geometrically can be modeled via a discretized Wheeler - De Witt equation. This allows a way of getting around the fact that conventional cosmological CMB is limited by a barrier as of a red shift limit of about z = 1000,as to photons, and to come up with a working model of quintessence scalar fields which permits relic generation of dark matter/dark energy as well as relic gravitons. |
1805.09206 | Carlos A. Batista da S. Filho | Carlos Batista and Gabriel Luz Almeida | A Class of Integrable Metrics II | 11 pages | Phys. Rev. D 98, 044030 (2018) | 10.1103/PhysRevD.98.044030 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting with a subclass of the four-dimensional spaces possessing two
commuting Killing vectors and a non-trivial Killing tensor, we fully integrate
Einstein's vacuum equation with a cosmological constant. Although most of the
solutions happen to be already known, we have found a solution that, as far as
we could search for, has not been attained before. We also characterize the
geometric properties of this new solution, it is a Kundt spacetime of Petrov
type II possessing a null Killing vector field and an isometry algebra that is
three-dimensional and abelian. In particular, such solution becomes a pp-wave
spacetime when the cosmological constant is set to zero.
| [
{
"created": "Wed, 23 May 2018 14:52:29 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Batista",
"Carlos",
""
],
[
"Almeida",
"Gabriel Luz",
""
]
] | Starting with a subclass of the four-dimensional spaces possessing two commuting Killing vectors and a non-trivial Killing tensor, we fully integrate Einstein's vacuum equation with a cosmological constant. Although most of the solutions happen to be already known, we have found a solution that, as far as we could search for, has not been attained before. We also characterize the geometric properties of this new solution, it is a Kundt spacetime of Petrov type II possessing a null Killing vector field and an isometry algebra that is three-dimensional and abelian. In particular, such solution becomes a pp-wave spacetime when the cosmological constant is set to zero. |
1912.06471 | Alesandro Santos | W. A. G. De Moraes and A. F. Santos | Lagrangian formalism for Rastall theory of gravity and G\"{o}del-type
universe | 18 pages, accepted for publication in GRG | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Rastall gravity a non-minimal coupling between geometry and matter
fields is considered. Then the usual energy-momentum tensor conservation law is
not valid. Here a Lagrangian formalism is proposed to the Rastall theory of
gravity. The G\"{o}del-type universe is studied in this gravitational model.
Then it is studied whether this theory permits causality violation. The field
equations do not exclude solutions with a breakdown of causality for a perfect
fluid as matter content. In this case, an expression for the critical radius
(beyond which the causality is violated) is determined. In addition, for a
combination between perfect fluid and scalar field as matter content the theory
accommodates causal G\"{o}del-type solution.
| [
{
"created": "Tue, 10 Dec 2019 15:18:15 GMT",
"version": "v1"
}
] | 2019-12-16 | [
[
"De Moraes",
"W. A. G.",
""
],
[
"Santos",
"A. F.",
""
]
] | In the Rastall gravity a non-minimal coupling between geometry and matter fields is considered. Then the usual energy-momentum tensor conservation law is not valid. Here a Lagrangian formalism is proposed to the Rastall theory of gravity. The G\"{o}del-type universe is studied in this gravitational model. Then it is studied whether this theory permits causality violation. The field equations do not exclude solutions with a breakdown of causality for a perfect fluid as matter content. In this case, an expression for the critical radius (beyond which the causality is violated) is determined. In addition, for a combination between perfect fluid and scalar field as matter content the theory accommodates causal G\"{o}del-type solution. |
2006.05735 | Vardarajan Suneeta | Dhanya S.Menon, Vardarajan Suneeta | Nonlinear perturbations of higher dimensional anti-de Sitter spacetime | 43 pages, discussion expanded, numerical factor missed in a
Mathematica file related to previous version corrected, thanks to referees
for their comments that led to correction. Resonant terms now vanish at
second order for cases studied | Phys. Rev. D 102, 104026 (2020) | 10.1103/PhysRevD.102.104026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study nonlinear gravitational perturbations of vacuum Einstein equations,
with $\Lambda<0$ in $(n+2)$ dimensions, with $n>2$, generalizing previous
studies for $n=2$. We follow the formalism by Ishibashi, Kodama and Seto to
decompose the metric perturbations into tensor, vector and scalar sectors, and
simplify the Einstein equations. The tensor perturbations are the new feature
of higher dimensions. We render the metric perturbations asymptotically anti-de
Sitter by employing a suitable gauge choice for each of the sectors. Finally,
we analyze the resonant structure of the perturbed equations at second order
for the five dimensional case, by a partial study of single mode tensor-type
perturbations at the linear level. For the cases we studied, resonant terms
vanish at second order.
| [
{
"created": "Wed, 10 Jun 2020 08:51:32 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Sep 2020 15:11:34 GMT",
"version": "v2"
}
] | 2020-11-18 | [
[
"Menon",
"Dhanya S.",
""
],
[
"Suneeta",
"Vardarajan",
""
]
] | We study nonlinear gravitational perturbations of vacuum Einstein equations, with $\Lambda<0$ in $(n+2)$ dimensions, with $n>2$, generalizing previous studies for $n=2$. We follow the formalism by Ishibashi, Kodama and Seto to decompose the metric perturbations into tensor, vector and scalar sectors, and simplify the Einstein equations. The tensor perturbations are the new feature of higher dimensions. We render the metric perturbations asymptotically anti-de Sitter by employing a suitable gauge choice for each of the sectors. Finally, we analyze the resonant structure of the perturbed equations at second order for the five dimensional case, by a partial study of single mode tensor-type perturbations at the linear level. For the cases we studied, resonant terms vanish at second order. |
1110.3448 | Guoying Chee | Guo-Ying Qi, Yongxin Guo | A exact de Sitter cosmological solution of quadratic gravitation with
torsion | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A exact de Sitter-like cosmological solution of quadratic gravitation with
torsion has been found. In the limit of constant energy and pressure, it
becomes a exact de Sitter spacetime. It exists in a wide class of quadratic
gravity theories and is the same in vacuum for all the models in this class, no
matter how the coefficients of the quadratic terms in the Lagrangian are. It
describes an accelerating universe and gives a cosmological constant which is
of the order of magnitude of the observed value. In vacuum the universe is a de
Sitter spacetime without torsion. When matter presents, however, the spacetime
is equipped with curvature as well as torsion. In other wards torsion can be
generated by the energy-momentum of matter (energy and pressure).
| [
{
"created": "Sun, 16 Oct 2011 01:50:10 GMT",
"version": "v1"
}
] | 2011-10-18 | [
[
"Qi",
"Guo-Ying",
""
],
[
"Guo",
"Yongxin",
""
]
] | A exact de Sitter-like cosmological solution of quadratic gravitation with torsion has been found. In the limit of constant energy and pressure, it becomes a exact de Sitter spacetime. It exists in a wide class of quadratic gravity theories and is the same in vacuum for all the models in this class, no matter how the coefficients of the quadratic terms in the Lagrangian are. It describes an accelerating universe and gives a cosmological constant which is of the order of magnitude of the observed value. In vacuum the universe is a de Sitter spacetime without torsion. When matter presents, however, the spacetime is equipped with curvature as well as torsion. In other wards torsion can be generated by the energy-momentum of matter (energy and pressure). |
1306.0317 | Piotr Bizon | Piotr Bizo\'n and Joanna Ja{\l}mu\.zna | Globally regular instability of $AdS_3$ | 5 pages, 4 figures. Dedicated to Professor Andrzej Staruszkiewicz on
the occasion of the 50th anniversary of his pioneering work on
three-dimensional gravity | Phys. Rev. Lett. 111, 041102 (2013) | 10.1103/PhysRevLett.111.041102 | null | gr-qc hep-th math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider three-dimensional AdS gravity minimally coupled to a massless
scalar field and study numerically the evolution of small smooth circularly
symmetric perturbations of the $AdS_3$ spacetime. As in higher dimensions, for
a large class of perturbations, we observe a turbulent cascade of energy to
high frequencies which entails instability of $AdS_3$. However, in contrast to
higher dimensions, the cascade cannot be terminated by black hole formation
because small perturbations have energy below the black hole threshold. This
situation appears to be challenging for the cosmic censor. Analysing the energy
spectrum of the cascade we determine the width $\rho(t)$ of the analyticity
strip of solutions in the complex spatial plane and argue by extrapolation that
$\rho(t)$ does not vanish in finite time. This provides evidence that the
turbulence is too weak to produce a naked singularity and the solutions remain
globally regular in time, in accordance with the cosmic censorship hypothesis.
| [
{
"created": "Mon, 3 Jun 2013 08:14:34 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Bizoń",
"Piotr",
""
],
[
"Jałmużna",
"Joanna",
""
]
] | We consider three-dimensional AdS gravity minimally coupled to a massless scalar field and study numerically the evolution of small smooth circularly symmetric perturbations of the $AdS_3$ spacetime. As in higher dimensions, for a large class of perturbations, we observe a turbulent cascade of energy to high frequencies which entails instability of $AdS_3$. However, in contrast to higher dimensions, the cascade cannot be terminated by black hole formation because small perturbations have energy below the black hole threshold. This situation appears to be challenging for the cosmic censor. Analysing the energy spectrum of the cascade we determine the width $\rho(t)$ of the analyticity strip of solutions in the complex spatial plane and argue by extrapolation that $\rho(t)$ does not vanish in finite time. This provides evidence that the turbulence is too weak to produce a naked singularity and the solutions remain globally regular in time, in accordance with the cosmic censorship hypothesis. |
0802.2450 | Z. Ya. Turakulov | A.T. Muminov | Motion of Spin 1/2 Massless Particle in a Curved Spacetime. I.
Lagrangian Approach | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-classical picture of motion of spin 1/2 massless particle in a curved
spacetime is built on base of simple Lagrangian model. The one is constructed
due to analogy with Lagrangian of massive spin 1/2 particle. Equations of
motion and spin propagation coincide with Papapetrou equations describing
dynamic of photon in a curved spacetime.
| [
{
"created": "Mon, 18 Feb 2008 10:31:45 GMT",
"version": "v1"
}
] | 2008-02-19 | [
[
"Muminov",
"A. T.",
""
]
] | Quasi-classical picture of motion of spin 1/2 massless particle in a curved spacetime is built on base of simple Lagrangian model. The one is constructed due to analogy with Lagrangian of massive spin 1/2 particle. Equations of motion and spin propagation coincide with Papapetrou equations describing dynamic of photon in a curved spacetime. |
1804.11106 | Dirk Puetzfeld | Dirk Puetzfeld, Yuri N. Obukhov | Deviation equation in Riemann-Cartan spacetime | 9 pages, 1 figure | Phys. Rev. D 97, 104069 (2018) | 10.1103/PhysRevD.97.104069 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a generalized deviation equation in Riemann-Cartan spacetime. The
equation describes the dynamics of the connecting vector which links events on
two general adjacent world lines. Our result is valid for any theory in a
Riemann-Cartan background, in particular, it is applicable to a large class of
gravitational theories which go beyond the general relativistic framework.
| [
{
"created": "Mon, 30 Apr 2018 09:55:39 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jun 2018 09:57:46 GMT",
"version": "v2"
}
] | 2018-06-05 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] | We derive a generalized deviation equation in Riemann-Cartan spacetime. The equation describes the dynamics of the connecting vector which links events on two general adjacent world lines. Our result is valid for any theory in a Riemann-Cartan background, in particular, it is applicable to a large class of gravitational theories which go beyond the general relativistic framework. |
2201.06739 | Paxy George Dr | Paxy George | Holographic Ricci DE as running vacuum with nonlinear interactions | 18 pages, 12 figures | null | 10.1142/S021827182250122X | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The holographic Ricci dark energy can be treated as a running vacuum due to
its analogy in the energy density, which is a combination of $H$ and $\dot H$,
the model can predict either eternal acceleration or eternal deceleration. In
the earlier works, we have shown that the presence of additive constant in the
energy density or by considering possible interaction between dark sectors
through a phenomenological term, the model can predict a transition from a
prior decelerated to a late accelerated epoch. This paper analyses the cosmic
evolution of holographic Ricci dark energy as a running vacuum with a nonlinear
interaction between dark sectors in a flat FLRW universe. We consider three
possible nonlinear interaction forms which give analytically feasible
solutions. We have constrained the model using the Type1a
Supernova(Pantheon)+CMB(Planck 2018)+BAO(SDSS) data and evaluated the
best-estimated values of all the model parameters. We have analyzed the
evolution of the Hubble parameter and deceleration parameter of all three
cases. We perform state finder analysis of the model, which implies the
quintessence nature of the model and found that it is distinguishably different
from the standard $\Lambda$CDM model. The dynamical system analysis of all
three cases confirms the evolution of the universe from an unstable prior
matter-dominated era to a stable end de Sitter phase.
| [
{
"created": "Tue, 18 Jan 2022 04:36:06 GMT",
"version": "v1"
}
] | 2023-01-25 | [
[
"George",
"Paxy",
""
]
] | The holographic Ricci dark energy can be treated as a running vacuum due to its analogy in the energy density, which is a combination of $H$ and $\dot H$, the model can predict either eternal acceleration or eternal deceleration. In the earlier works, we have shown that the presence of additive constant in the energy density or by considering possible interaction between dark sectors through a phenomenological term, the model can predict a transition from a prior decelerated to a late accelerated epoch. This paper analyses the cosmic evolution of holographic Ricci dark energy as a running vacuum with a nonlinear interaction between dark sectors in a flat FLRW universe. We consider three possible nonlinear interaction forms which give analytically feasible solutions. We have constrained the model using the Type1a Supernova(Pantheon)+CMB(Planck 2018)+BAO(SDSS) data and evaluated the best-estimated values of all the model parameters. We have analyzed the evolution of the Hubble parameter and deceleration parameter of all three cases. We perform state finder analysis of the model, which implies the quintessence nature of the model and found that it is distinguishably different from the standard $\Lambda$CDM model. The dynamical system analysis of all three cases confirms the evolution of the universe from an unstable prior matter-dominated era to a stable end de Sitter phase. |
0909.2487 | Nima Khosravi | N. Khosravi, H. R. Sepangi, B. Vakili | A cosmological viewpoint on the correspondence between deformed
phase-space and canonical quantization | 19 pages, 31 figures; This paper is a complement to arXiv:0903.1914; | Gen.Rel.Grav.42:1081-1102,2010 | 10.1007/s10714-009-0894-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We employ the familiar canonical quantization procedure in a given
cosmological setting to argue that it is equivalent to and results in the same
physical picture if one considers the deformation of the phase-space instead.
To show this we use a Probabilistic Evolutionary Process (PEP) to make the
solutions of these different approaches comparable. Specific model theories are
used to show that the independent solutions of the resulting Wheeler-DeWitt
equation are equivalent to solutions of the deformation method with different
signs for the deformation parameter. We also argued that since the
Wheeler-DeWitt equation is a direct consequence of diffeomorphism invariance,
this equivalence is only true provided that the deformation of phase-space does
not break such an invariance.
| [
{
"created": "Mon, 14 Sep 2009 08:23:30 GMT",
"version": "v1"
},
{
"created": "Tue, 18 May 2010 06:08:27 GMT",
"version": "v2"
}
] | 2010-05-25 | [
[
"Khosravi",
"N.",
""
],
[
"Sepangi",
"H. R.",
""
],
[
"Vakili",
"B.",
""
]
] | We employ the familiar canonical quantization procedure in a given cosmological setting to argue that it is equivalent to and results in the same physical picture if one considers the deformation of the phase-space instead. To show this we use a Probabilistic Evolutionary Process (PEP) to make the solutions of these different approaches comparable. Specific model theories are used to show that the independent solutions of the resulting Wheeler-DeWitt equation are equivalent to solutions of the deformation method with different signs for the deformation parameter. We also argued that since the Wheeler-DeWitt equation is a direct consequence of diffeomorphism invariance, this equivalence is only true provided that the deformation of phase-space does not break such an invariance. |
1707.06994 | Marie-No\"elle C\'el\'erier | M.-N. C\'el\'erier, N. O. Santos, V. H. Satheeshkumar | Hilbert repulsion in the Reissner-Nordstr\"om and Schwarzschild
spacetimes | 10 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Studying particle motion in the gravitational field of a black hole from the
perspective of different observers is important for separating the coordinate
artifacts from the physical phenomena. In this paper, we show that a freely
falling test particle exhibits gravitational repulsion by a black hole as seen
by an asymptotic observer, whereas nothing of the kind happens as recorded by a
freely falling observer or by an observer located at a finite distance from the
event horizon. This analysis is carried out for a general Reissner-Nordstr\"om,
an extremal Reissner-Nordstr\"om, and a Schwarzschild black hole. We are lead
to conclude that the origin of these bizarre results lies in the fact that the
quantities measured by the different observers are neither Lorentz scalars nor
gauge invariant.
| [
{
"created": "Fri, 21 Jul 2017 08:17:24 GMT",
"version": "v1"
}
] | 2017-07-25 | [
[
"Célérier",
"M. -N.",
""
],
[
"Santos",
"N. O.",
""
],
[
"Satheeshkumar",
"V. H.",
""
]
] | Studying particle motion in the gravitational field of a black hole from the perspective of different observers is important for separating the coordinate artifacts from the physical phenomena. In this paper, we show that a freely falling test particle exhibits gravitational repulsion by a black hole as seen by an asymptotic observer, whereas nothing of the kind happens as recorded by a freely falling observer or by an observer located at a finite distance from the event horizon. This analysis is carried out for a general Reissner-Nordstr\"om, an extremal Reissner-Nordstr\"om, and a Schwarzschild black hole. We are lead to conclude that the origin of these bizarre results lies in the fact that the quantities measured by the different observers are neither Lorentz scalars nor gauge invariant. |
1901.06206 | Andrea Giusti | R. Casadio, A. Giusti, A. Mentrelli | Orbits in a stochastic Schwarzschild geometry | REVTeX 23 pages, 20 figures | Phys. Rev. D 100, 024036 (2019) | 10.1103/PhysRevD.100.024036 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study geodesics in the Schwarzschild space-time affected by an uncertainty
in the mass parameter described by a Gaussian distribution. This study could
serve as a first attempt at investigating possible quantum effects of black
hole space-times on the motion of matter in their surroundings as well as the
role of uncertainties in the measurement of the black hole parameters.
| [
{
"created": "Fri, 18 Jan 2019 12:42:40 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jul 2019 15:49:18 GMT",
"version": "v2"
}
] | 2019-07-24 | [
[
"Casadio",
"R.",
""
],
[
"Giusti",
"A.",
""
],
[
"Mentrelli",
"A.",
""
]
] | We study geodesics in the Schwarzschild space-time affected by an uncertainty in the mass parameter described by a Gaussian distribution. This study could serve as a first attempt at investigating possible quantum effects of black hole space-times on the motion of matter in their surroundings as well as the role of uncertainties in the measurement of the black hole parameters. |
2305.04336 | Shafqat Ul Islam | Jitendra Kumar, Shafqat Ul Islam and Sushant G. Ghosh | Strong Gravitational Lensing by Loop Quantum Gravity Motivated Rotating
Black Holes and EHT Observations | 16 Pages, 11 Figures, 3 Tables, Accepted for publication in EPJC | null | null | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We investigate gravitational lensing in the strong deflection regime by loop
quantum gravity (LQG)-motivated rotating black hole (LMRBH) metrics with an
additional parameter $l$ besides mass $M$ and rotation $a$. The LMRBH
spacetimes are regular everywhere, asymptotically encompassing the Kerr black
hole as a particular case and, depending on the parameters, describe black
holes with one horizon only (BH-I), black holes with an event horizon and a
Cauchy horizon (BH-II), black holes with three horizons (BH-III), or black
holes with no horizons (NH) spacetime. It turns out that as the LQG parameter
$l$ increases, the unstable photon orbit radius $x_{ps}$, the critical impact
parameter $u_{ps}$, the deflection angle $\alpha_D(\theta)$ and angular
position $\theta_{\infty}$ also increases. Meanwhile, the angular separation
$s$ decreases, and relative magnitude $r_{mag}$ increases with increasing $l$
for prograde motion but they show opposite behaviour for the retrograde motion.
For Sgr A*, the angular position $\theta_{\infty}$ is $\in$ (16.4, 39.8)
$\mu$as, while for M87* $\in$ (12.33, 29.9) $\mu$as. The angular separation
$s$, for SMBHs Sgr A* and M87*, differs significantly, with values ranging
$\in$ (0.008-0.376) $\mu$as for Sgr A* and $\in$ (0.006-0.282) $\mu$as for
M87*. We estimate the time delay between the first and second relativistic
images using twenty supermassive galactic centre black holes as lenses. Our
analysis concludes that, within the $1 \sigma$ region, a significant portion of
the BH-I and BH-II and for a small portion of BH-III parameter space agrees
with the EHT results of M87* and Sgr A* whereas NH is completely ruled out. We
discover that the EHT results of Sgr A* place more stringent limits on the
parameter space of LMRBH black holes than those established by the EHT results
of M87*.
| [
{
"created": "Sun, 7 May 2023 17:26:54 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Oct 2023 04:17:48 GMT",
"version": "v2"
}
] | 2023-10-31 | [
[
"Kumar",
"Jitendra",
""
],
[
"Islam",
"Shafqat Ul",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | We investigate gravitational lensing in the strong deflection regime by loop quantum gravity (LQG)-motivated rotating black hole (LMRBH) metrics with an additional parameter $l$ besides mass $M$ and rotation $a$. The LMRBH spacetimes are regular everywhere, asymptotically encompassing the Kerr black hole as a particular case and, depending on the parameters, describe black holes with one horizon only (BH-I), black holes with an event horizon and a Cauchy horizon (BH-II), black holes with three horizons (BH-III), or black holes with no horizons (NH) spacetime. It turns out that as the LQG parameter $l$ increases, the unstable photon orbit radius $x_{ps}$, the critical impact parameter $u_{ps}$, the deflection angle $\alpha_D(\theta)$ and angular position $\theta_{\infty}$ also increases. Meanwhile, the angular separation $s$ decreases, and relative magnitude $r_{mag}$ increases with increasing $l$ for prograde motion but they show opposite behaviour for the retrograde motion. For Sgr A*, the angular position $\theta_{\infty}$ is $\in$ (16.4, 39.8) $\mu$as, while for M87* $\in$ (12.33, 29.9) $\mu$as. The angular separation $s$, for SMBHs Sgr A* and M87*, differs significantly, with values ranging $\in$ (0.008-0.376) $\mu$as for Sgr A* and $\in$ (0.006-0.282) $\mu$as for M87*. We estimate the time delay between the first and second relativistic images using twenty supermassive galactic centre black holes as lenses. Our analysis concludes that, within the $1 \sigma$ region, a significant portion of the BH-I and BH-II and for a small portion of BH-III parameter space agrees with the EHT results of M87* and Sgr A* whereas NH is completely ruled out. We discover that the EHT results of Sgr A* place more stringent limits on the parameter space of LMRBH black holes than those established by the EHT results of M87*. |
0812.1307 | Jean Alexandre | Jean Alexandre, Darrel Yawitch | Branon stabilization from fermion-induced radiative corrections | 7 pages | Phys.Lett.B676:184-187,2009 | 10.1016/j.physletb.2009.05.003 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a 3-brane embedded in 5-dimensional space time characterized by a
Gaussian warp factor, for which the four-dimensional effective theory for brane
fluctuation (branons) is unstable. We show that radiative corrections arising
from fermions living on the brane, and therefore coupled to branons, stabilize
the system by generating dynamically a spontaneous symmetry breaking for the
branon field. The price to pay, for the corresponding mechanism to be
consistent, is to have a large number of fermion flavours, and we discuss the
fat brane scenario as an interpretation for the dressed branon theory, taking
into account the Maxwell construction, which avoids the spinodal instability
present in the perturbative effective potential.
| [
{
"created": "Mon, 8 Dec 2008 15:56:17 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2009 11:27:37 GMT",
"version": "v2"
},
{
"created": "Thu, 7 May 2009 14:21:03 GMT",
"version": "v3"
}
] | 2009-05-29 | [
[
"Alexandre",
"Jean",
""
],
[
"Yawitch",
"Darrel",
""
]
] | We consider a 3-brane embedded in 5-dimensional space time characterized by a Gaussian warp factor, for which the four-dimensional effective theory for brane fluctuation (branons) is unstable. We show that radiative corrections arising from fermions living on the brane, and therefore coupled to branons, stabilize the system by generating dynamically a spontaneous symmetry breaking for the branon field. The price to pay, for the corresponding mechanism to be consistent, is to have a large number of fermion flavours, and we discuss the fat brane scenario as an interpretation for the dressed branon theory, taking into account the Maxwell construction, which avoids the spinodal instability present in the perturbative effective potential. |
gr-qc/9807067 | A. Dolgov | A.D. Dolgov and I.D. Novikov | Superluminal propagation of light in gravitational field and non-causal
signals | 18 pages, 4 figures, Latex | Phys.Lett. B442 (1998) 82-89 | 10.1016/S0370-2693(98)01223-4 | TAC-1998-018 | gr-qc hep-th | null | It has been found in several papers that, because of quantum corrections,
light front can propagate with superluminal velocity in gravitational fields
and even in flat space-time across two conducting plates. We show that, if this
is the case, closed time-like trajectories would be possible and, in
particular, in certain reference frames photons could return to their source of
origin before they were produced there, in contrast to the opposite claim made
in the literature.
| [
{
"created": "Thu, 23 Jul 1998 15:49:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dolgov",
"A. D.",
""
],
[
"Novikov",
"I. D.",
""
]
] | It has been found in several papers that, because of quantum corrections, light front can propagate with superluminal velocity in gravitational fields and even in flat space-time across two conducting plates. We show that, if this is the case, closed time-like trajectories would be possible and, in particular, in certain reference frames photons could return to their source of origin before they were produced there, in contrast to the opposite claim made in the literature. |
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