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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9611006 | Franz Embacher | Franz Embacher | Decomposition and unitarity in quantum cosmology | 44 pages, LaTeX (no figures), References on the predecessors of the
refined algebraic quantization program added, minor typos corrected | null | null | UWThPh-1996-64 | gr-qc | null | Considering quantum cosmological minisuperspace models with positive
potential, we present evidence that
(i) despite common belief there are perspectives for defining a unique,
naturally preferred decomposition of the space H of wave functions into two
subspaces H^\pm that generalizes the concept of positive and negative
frequency, and that
(ii) an underlying unitary evolution within these two subspaces exists and
may be described in analogy to the representation of a geometric object in
local coordinates: it is associated with the choice of a congruence of
classical trajectories endowed with a suitable weight (such a setting is called
WKB-branch).
The transformation properties of various quantities under a variation of the
WKB-branch provide the tool for defining the decomposition. The construction
leads to formal series whose actual convergence seems to require additional
conditions on the model (related to global geometric issues and possibly to
analyticity). It is speculated that this approach might relate to the refined
algebraic quantization program.
| [
{
"created": "Mon, 4 Nov 1996 18:26:25 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Dec 1996 12:52:04 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Embacher",
"Franz",
""
]
] | Considering quantum cosmological minisuperspace models with positive potential, we present evidence that (i) despite common belief there are perspectives for defining a unique, naturally preferred decomposition of the space H of wave functions into two subspaces H^\pm that generalizes the concept of positive and negative frequency, and that (ii) an underlying unitary evolution within these two subspaces exists and may be described in analogy to the representation of a geometric object in local coordinates: it is associated with the choice of a congruence of classical trajectories endowed with a suitable weight (such a setting is called WKB-branch). The transformation properties of various quantities under a variation of the WKB-branch provide the tool for defining the decomposition. The construction leads to formal series whose actual convergence seems to require additional conditions on the model (related to global geometric issues and possibly to analyticity). It is speculated that this approach might relate to the refined algebraic quantization program. |
1602.03839 | LVC Publications | 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, 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, K. Boh\'emier, 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, M. Cabero, 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,
J. H. Clayton, F. Cleva, E. Coccia, P.-F. Cohadon, T. Cokelaer, 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, T.
D. 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,
S. De, D. DeBra, G. Debreczeni, J. Degallaix, M. De Laurentis, S.
Del\'eglise, W. Del Pozzo, T. Denker, T. Dent, H. Dereli, V. Dergachev, R. T.
DeRosa, R. De Rosa, R. DeSalvo, S. Dhurandhar, M. C. D\'iaz, A. Dietz, 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, 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, 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, N. Fotopoulos,
J.-D. Fournier, S. Franco, S. Frasca, F. Frasconi, M. Frei, Z. Frei, A.
Freise, R. Frey, V. Frey, T. T. Fricke, P. Fritschel, V. V. Frolov, P. Fulda,
M. Fyffe, H. A. G. Gabbard, 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. M. Goggin, 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, 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, D. I. Jones, G. 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, D. G. Keppel, 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, J. E. Lord, M. Lorenzini, V. Loriette, M. Lormand, G. Losurdo, J.
D. Lough, H. L\"uck, A. P. Lundgren, J. Luo, R. Lynch, Y. Ma, T. MacDonald,
B. Machenschalk, M. MacInnis, D. M. Macleod, F. Magana-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. A. McKechan, 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, E. Messaritaki, 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. Parker, D.
Pascucci, A. Pasqualetti, R. Passaquieti, D. Passuello, B. Patricelli, Z.
Patrick, B. L. Pearlstone, M. Pedraza, R. Pedurand, L. Pekowsky, A. Pele, S.
Penn, A. Perreca, M. Phelps, O. Piccinni, M. Pichot, F. Piergiovanni, V.
Pierro, G. Pillant, L. Pinard, I. M. Pinto, M. Pitkin, R. Poggiani, P.
Popolizio, A. Post, J. Powell, J. Prasad, V. Predoi, S. S. Premachandra, T.
Prestegard, L. R. Price, M. Prijatelj, M. Principe, S. Privitera, G. A.
Prodi, L. Prokhorov, O. Puncken, M. Punturo, P. Puppo, M. P\"urrer, H. Qi, J.
Qin, V. Quetschke, E. A. Quintero, R. Quitzow-James, F. J. Raab, D. S.
Rabeling, H. Radkins, P. Raffai, S. Raja, M. Rakhmanov, P. Rapagnani, V.
Raymond, M. Razzano, V. Re, J. Read, C. M. Reed, T. Regimbau, L. Rei, S.
Reid, D. H. Reitze, H. Rew, S. D. Reyes, F. Ricci, K. Riles, N. A. Robertson,
R. Robie, F. Robinet, C. Robinson, A. Rocchi, A. C. Rodriguez, L. Rolland, J.
G. Rollins, V. J. Roma, R. Romano, G. Romanov, J. H. Romie, D. Rosi\'nska, S.
Rowan, A. R\"udiger, P. Ruggi, K. Ryan, S. Sachdev, T. Sadecki, L. Sadeghian,
L. Salconi, M. Saleem, F. Salemi, A. Samajdar, L. Sammut, E. J. Sanchez, V.
Sandberg, B. Sandeen, J. R. Sanders, L. Santamar\'ia, B. Sassolas, B. S.
Sathyaprakash, P. R. Saulson, O. Sauter, R. L. Savage, A. Sawadsky, P.
Schale, R. Schilling, J. Schmidt, P. Schmidt, R. Schnabel, R. M. S.
Schofield, A. Sch\"onbeck, E. Schreiber, D. Schuette, B. F. Schutz, J. Scott,
S. M. Scott, D. Sellers, A. S. Sengupta, D. Sentenac, V. Sequino, A. Sergeev,
G. Serna, Y. Setyawati, A. Sevigny, D. A. Shaddock, S. Shah, M. S. Shahriar,
M. Shaltev, Z. Shao, B. Shapiro, P. Shawhan, A. Sheperd, D. H. Shoemaker, D.
M. Shoemaker, K. Siellez, X. Siemens, D. Sigg, A. D. Silva, D. Simakov, A.
Singer, L. P. Singer, A. Singh, R. Singh, A. Singhal, A. M. Sintes, B. J. J.
Slagmolen, J. R. Smith, N. D. Smith, R. J. E. Smith, E. J. Son, B. Sorazu, F.
Sorrentino, T. Souradeep, A. K. Srivastava, A. Staley, M. Steinke, J.
Steinlechner, S. Steinlechner, D. Steinmeyer, B. C. Stephens, R. Stone, K. A.
Strain, N. Straniero, G. Stratta, N. A. Strauss, S. Strigin, R. Sturani, A.
L. Stuver, T. Z. Summerscales, L. Sun, P. J. Sutton, B. L. Swinkels, M. J.
Szczepa\'nczyk, M. Tacca, D. Talukder, D. B. Tanner, M. T\'apai, S. P.
Tarabrin, A. Taracchini, R. Taylor, T. Theeg, M. P. Thirugnanasambandam, E.
G. Thomas, M. Thomas, P. Thomas, K. A. Thorne, K. S. Thorne, E. Thrane, S.
Tiwari, V. Tiwari, K. V. Tokmakov, C. Tomlinson, M. Tonelli, C. V. Torres, C.
I. Torrie, D. T\"oyr\"a, F. Travasso, G. Traylor, D. Trifir\`o, M. C.
Tringali, L. Trozzo, M. Tse, M. Turconi, D. Tuyenbayev, D. Ugolini, C. S.
Unnikrishnan, A. L. Urban, S. A. Usman, H. Vahlbruch, G. Vajente, G. Valdes,
N. van Bakel, M. van Beuzekom, J. F. J. van den Brand, C. Van Den Broeck, D.
C. Vander-Hyde, L. van der Schaaf, J. V. van Heijningen, A. A. van Veggel, M.
Vardaro, S. Vass, M. Vas\'uth, R. Vaulin, A. Vecchio, G. Vedovato, J. Veitch,
P. J. Veitch, K. Venkateswara, D. Verkindt, F. Vetrano, A. Vicer\'e, S.
Vinciguerra, D. J. Vine, J.-Y. Vinet, S. Vitale, T. Vo, H. Vocca, C. Vorvick,
D. Voss, W. D. Vousden, S. P. Vyatchanin, A. R. Wade, L. E. Wade, M. Wade, M.
Walker, L. Wallace, S. Walsh, G. Wang, H. Wang, M. Wang, X. Wang, Y. Wang, R.
L. Ward, J. Warner, M. Was, B. Weaver, L.-W. Wei, M. Weinert, A. J.
Weinstein, R. Weiss, T. Welborn, L. Wen, P. We{\ss}els, M. West, T. Westphal,
K. Wette, J. T. Whelan, D. J. White, B. F. Whiting, K. Wiesner, R. D.
Williams, A. R. Williamson, J. L. Willis, B. Willke, M. H. Wimmer, W.
Winkler, C. C. Wipf, A. G. Wiseman, 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 | GW150914: First results from the search for binary black hole
coalescence with Advanced LIGO | 20 pages, 10 figures | Phys. Rev. D 93, 122003 (2016) | 10.1103/PhysRevD.93.122003 | LIGO-P1500269 | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser
Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed
the binary black hole merger GW150914. We report the results of a
matched-filter search using relativistic models of compact-object binaries that
recovered GW150914 as the most significant event during the coincident
observations between the two LIGO detectors from September 12 to October 20,
2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24
and a false alarm rate estimated to be less than 1 event per 203 000 years,
equivalent to a significance greater than 5.1 {\sigma}.
| [
{
"created": "Thu, 11 Feb 2016 19:26:46 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2016 18:26:03 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Apr 2016 08:39:35 GMT",
"version": "v3"
}
] | 2016-08-06 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
],
[
"Abbott",
"B. P.",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T. D.",
""
],
[
"Abernathy",
"M. R.",
""
],
[
"Acernese",
"F... | On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1 {\sigma}. |
2308.16430 | Pramit Rej | Pramit Rej and Piyali Bhar | Relativistic isotropic stellar model in $f(R,\,T)$ gravity with
Durgapal- IV Metric | 17 pages, 9 figures, 2 tables. arXiv admin note: text overlap with
arXiv:2212.07810 | New Astronomy, Volume 105, January 2024, 102113 | 10.1016/j.newast.2023.102113 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, a new static, non-singular, spherically symmetric fluid model
has been obtained in the background of $f(R,\,T)$ gravity. Here we consider the
isotropic metric potentials of Durgapal-IV [M.C. Durgapal, J. Phys. A {\bf 15}
2637 (1982)] solution as input to handle the Einstein field equations in
$f(R,\,T)$ environment. For different coupling parameter values of $\chi$,
graphical representations of the physical parameters have been demonstrated to
describe the analytical results more clearly. It should be highlighted that the
results of General Relativity (GR) are given by $\chi=0$. With the use of both
analytical discussion and graphical illustrations, a thorough comparison of our
results with the GR outcomes is also covered. The numerical values of the
various physical attributes have been given for various coupling parameter
$\chi$ values in order to discuss the impact of this parameter. Here we apply
our solution by considering the compact star candidate LMC X-4 [M.L. Rawls et
al., Astrophys. J. {\bf 730} 25 (2011)] with mass$=(1.04 \pm 0.09)M_{\odot}$
and radius $= 8.301_{-0.2}^{+0.2}$ km. respectively, to analyze both
analytically and graphically. To confirm the physical acceptance of our model,
we discuss certain physical properties of our obtained solution such as energy
conditions, causality, hydrostatic equilibrium through a modified
Tolman-Oppenheimer-Volkoff (TOV) conservation equation, pressure-density ratio,
etc. Also, our solution is well-behaved and free from any singularity at the
center. From our present study, it is observed that all of our obtained results
fall within the physically admissible regime, indicating the viability of our
model.
| [
{
"created": "Thu, 31 Aug 2023 03:37:30 GMT",
"version": "v1"
}
] | 2023-09-04 | [
[
"Rej",
"Pramit",
""
],
[
"Bhar",
"Piyali",
""
]
] | In this work, a new static, non-singular, spherically symmetric fluid model has been obtained in the background of $f(R,\,T)$ gravity. Here we consider the isotropic metric potentials of Durgapal-IV [M.C. Durgapal, J. Phys. A {\bf 15} 2637 (1982)] solution as input to handle the Einstein field equations in $f(R,\,T)$ environment. For different coupling parameter values of $\chi$, graphical representations of the physical parameters have been demonstrated to describe the analytical results more clearly. It should be highlighted that the results of General Relativity (GR) are given by $\chi=0$. With the use of both analytical discussion and graphical illustrations, a thorough comparison of our results with the GR outcomes is also covered. The numerical values of the various physical attributes have been given for various coupling parameter $\chi$ values in order to discuss the impact of this parameter. Here we apply our solution by considering the compact star candidate LMC X-4 [M.L. Rawls et al., Astrophys. J. {\bf 730} 25 (2011)] with mass$=(1.04 \pm 0.09)M_{\odot}$ and radius $= 8.301_{-0.2}^{+0.2}$ km. respectively, to analyze both analytically and graphically. To confirm the physical acceptance of our model, we discuss certain physical properties of our obtained solution such as energy conditions, causality, hydrostatic equilibrium through a modified Tolman-Oppenheimer-Volkoff (TOV) conservation equation, pressure-density ratio, etc. Also, our solution is well-behaved and free from any singularity at the center. From our present study, it is observed that all of our obtained results fall within the physically admissible regime, indicating the viability of our model. |
0809.4879 | Anzhong Wang | P. Rocha, R. Chan, M.F.A. da Silva, and Anzhong Wang | Stable and "bounded excursion" gravastars, and black holes in Einstein's
theory of gravity | revtex4, 24 figures, new references added. To appear in JCAP | JCAP 0811:010,2008 | 10.1088/1475-7516/2008/11/010 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical models of prototype gravastars are constructed and studied. The
models are the Visser-Wiltshire three-layer gravastars, in which an infinitely
thin spherical shell of a perfect fluid with the equation of state $p =
(1-\gamma)\sigma$ divides the whole spacetime into two regions, where the
internal region is de Sitter, and the external is Schwarzschild. When $\gamma <
1$ and $\Lambda \not= 0$, it is found that in some cases the models represent
stable gravastars, and in some cases they represent "bounded excursion" stable
gravastars, where the thin shell is oscillating between two finite radii, while
in some other cases they collapse until the formation of black holes. However,
when $\gamma \ge 1$, even with $\Lambda \not= 0$, only black holes are found.
In the phase space, the region for both stable gravastars and "bounded
excursion" gravastars is very small in comparison to that of black holes,
although it is not completely empty.
| [
{
"created": "Mon, 29 Sep 2008 00:38:17 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Oct 2008 01:41:55 GMT",
"version": "v2"
}
] | 2009-03-27 | [
[
"Rocha",
"P.",
""
],
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Wang",
"Anzhong",
""
]
] | Dynamical models of prototype gravastars are constructed and studied. The models are the Visser-Wiltshire three-layer gravastars, in which an infinitely thin spherical shell of a perfect fluid with the equation of state $p = (1-\gamma)\sigma$ divides the whole spacetime into two regions, where the internal region is de Sitter, and the external is Schwarzschild. When $\gamma < 1$ and $\Lambda \not= 0$, it is found that in some cases the models represent stable gravastars, and in some cases they represent "bounded excursion" stable gravastars, where the thin shell is oscillating between two finite radii, while in some other cases they collapse until the formation of black holes. However, when $\gamma \ge 1$, even with $\Lambda \not= 0$, only black holes are found. In the phase space, the region for both stable gravastars and "bounded excursion" gravastars is very small in comparison to that of black holes, although it is not completely empty. |
1201.5647 | Diego S\'aez-G\'omez | A. J. L\'opez-Revelles, Ratbay Myrzakulov, Diego S\'aez-G\'omez | Ekpyrotic universes in $F(R)$ Ho\v{r}ava-Lifshitz gravity | 12 pages. Version to be published in PRD | Phys. Rev. D 85: 103521, 2012 | 10.1103/PhysRevD.85.103521 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Ekpyrotic scenario is studied in the context of some extensions of
Ho\v{r}ava-Lifshitz gravity. Some particular solutions that lead to cyclic
Hubble parameters are analyzed, where the corresponding gravitational actions
are reconstructed by using several techniques and auxiliary fields. Its
comparison with standard $F(R)$ gravity is performed. In addition, the
so-called Little Rip, a stage of the universe evolution when some bounded
systems may be dissolute, is also studied in this frame of theories.
| [
{
"created": "Thu, 26 Jan 2012 21:02:38 GMT",
"version": "v1"
},
{
"created": "Wed, 16 May 2012 14:25:41 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"López-Revelles",
"A. J.",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Sáez-Gómez",
"Diego",
""
]
] | The Ekpyrotic scenario is studied in the context of some extensions of Ho\v{r}ava-Lifshitz gravity. Some particular solutions that lead to cyclic Hubble parameters are analyzed, where the corresponding gravitational actions are reconstructed by using several techniques and auxiliary fields. Its comparison with standard $F(R)$ gravity is performed. In addition, the so-called Little Rip, a stage of the universe evolution when some bounded systems may be dissolute, is also studied in this frame of theories. |
1012.4390 | Charmousis | Yannis Bardoux, Christos Charmousis and Theodoros Kolyvaris | Lovelock solutions in the presence of matter sources | Regular article, no figures, 29 pages | Phys.Rev.D83:104020,2011 | 10.1103/PhysRevD.83.104020 | LPT 10-102 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a large class of space and time-dependent warped geometries we find the
general solution of the 6-dimensional Einstein-Gauss-Bonnet equations in the
presence of p-form matter fields. This is done under two conditions on the
matter sector which we show impose the integrability of the full system.
Solutions are classified and known black hole limits are found. It is shown
that Lovelock gravity restricts drastically the possible horizon geometries and
allowed matter sources. In fact, we show that if we allow only for solutions of
asymptotically flat falloff behaviour, and no fine-tuning of coupling
constants, then the only permissible black hole is that of Boulware-Deser with
electromagnetic charge. The situation of 6 dimensional Lovelock gravity is
therefore almost identical to 4 dimensional General Relativity. The
gravitational horizon constraints lead us to find static solutions involving
3-form matter fields in anti de-Sitter space which are also new to General
Relativity along with other cosmological and black string type of solutions.
| [
{
"created": "Mon, 20 Dec 2010 16:33:18 GMT",
"version": "v1"
}
] | 2011-05-19 | [
[
"Bardoux",
"Yannis",
""
],
[
"Charmousis",
"Christos",
""
],
[
"Kolyvaris",
"Theodoros",
""
]
] | For a large class of space and time-dependent warped geometries we find the general solution of the 6-dimensional Einstein-Gauss-Bonnet equations in the presence of p-form matter fields. This is done under two conditions on the matter sector which we show impose the integrability of the full system. Solutions are classified and known black hole limits are found. It is shown that Lovelock gravity restricts drastically the possible horizon geometries and allowed matter sources. In fact, we show that if we allow only for solutions of asymptotically flat falloff behaviour, and no fine-tuning of coupling constants, then the only permissible black hole is that of Boulware-Deser with electromagnetic charge. The situation of 6 dimensional Lovelock gravity is therefore almost identical to 4 dimensional General Relativity. The gravitational horizon constraints lead us to find static solutions involving 3-form matter fields in anti de-Sitter space which are also new to General Relativity along with other cosmological and black string type of solutions. |
1912.12757 | Alexandros Karam Dr. | Ignatios Antoniadis, Alexandros Karam, Angelos Lykkas, Thomas Pappas,
Kyriakos Tamvakis | Single-field inflation in models with an $R^2$ term | 18 pages, 7 figures, invited talk given at Corfu Summer Institute
2019 "School and Workshops on Elementary Particle Physics and Gravity", 31
August - 25 September 2019, Corfu, Greece | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present two cases where the addition of the $R^2$ term to an inflationary
model leads to single-field inflation instead of two-field inflation as is
usually the case. In both cases we find that the effect of the $R^2$ term is to
reduce the value of the tensor-to-scalar ratio $r$.
| [
{
"created": "Sun, 29 Dec 2019 23:28:31 GMT",
"version": "v1"
}
] | 2020-01-01 | [
[
"Antoniadis",
"Ignatios",
""
],
[
"Karam",
"Alexandros",
""
],
[
"Lykkas",
"Angelos",
""
],
[
"Pappas",
"Thomas",
""
],
[
"Tamvakis",
"Kyriakos",
""
]
] | We present two cases where the addition of the $R^2$ term to an inflationary model leads to single-field inflation instead of two-field inflation as is usually the case. In both cases we find that the effect of the $R^2$ term is to reduce the value of the tensor-to-scalar ratio $r$. |
1207.4815 | Gonzalo Olmo | Gonzalo J. Olmo | Cosmology in Palatini theories of gravity | 16 pages, no figures. Contribution to the Proceedings of Spanish
Relativity Meeting ERE2011, Madrid 29 August - 2 September 2011 . Plenary
talk | AIP Conf. Proc. 1458 (2011), 222-237 | 10.1063/1.4734415 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss recent results on the cosmology of extended theories of gravity
formulated in the Palatini approach, i.e., assuming that metric and connection
are independent fields. In particular, we focus on the attempts to explain the
cosmic speedup with f(R) theories and on models that avoid the big bang
singularity. The field equations for gravity Lagrangians of the form
f(g_{\mu\nu},{R^\alpha}_{\beta\mu\nu}) (including torsion) are explicitly
derived and discussed.
| [
{
"created": "Thu, 19 Jul 2012 21:47:15 GMT",
"version": "v1"
}
] | 2012-07-23 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | We discuss recent results on the cosmology of extended theories of gravity formulated in the Palatini approach, i.e., assuming that metric and connection are independent fields. In particular, we focus on the attempts to explain the cosmic speedup with f(R) theories and on models that avoid the big bang singularity. The field equations for gravity Lagrangians of the form f(g_{\mu\nu},{R^\alpha}_{\beta\mu\nu}) (including torsion) are explicitly derived and discussed. |
1208.3306 | Tushar Kanti Dey | Tushar Kanti Dey | Strong gravitational lensing by Schwarzschild black hole | 4 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Schwarzschild black holes can produce strong gravitational lensing. The
relativistic images are produced due to bending of light around the black hole.
We propose a model equation to study the strong gravitational lensing. The
model equation can well describe the bending angle from a range very close to
the photon sphere to the first relativistic image.
| [
{
"created": "Thu, 16 Aug 2012 07:37:44 GMT",
"version": "v1"
}
] | 2012-08-17 | [
[
"Dey",
"Tushar Kanti",
""
]
] | Schwarzschild black holes can produce strong gravitational lensing. The relativistic images are produced due to bending of light around the black hole. We propose a model equation to study the strong gravitational lensing. The model equation can well describe the bending angle from a range very close to the photon sphere to the first relativistic image. |
1412.7263 | Taeyoon Moon | Yun Soo Myung and Taeyoon Moon | Scale-invariant spectrum of Lee-Wick model in de Sitter spacetime | 1+11 pages, no figures | null | 10.1088/1475-7516/2015/02/044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a scale-invariant spectrum from the Lee-Wick model in de Sitter
spacetime. This model is a fourth-order scalar theory whose mass parameter is
determined by $M^2=2H^2$. The Harrison-Zel'dovich scale-invariant spectrum is
obtained by Fourier transforming the propagator in position space as well as by
computing the power spectrum directly. It shows clearly that the LW scalar
theory provides a truly scale-invariant spectrum in whole de Sitter, while the
massless scalar propagation in de Sitter shows a scale-invariant spectrum in
the superhorizon region only.
| [
{
"created": "Tue, 23 Dec 2014 06:34:42 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We obtain a scale-invariant spectrum from the Lee-Wick model in de Sitter spacetime. This model is a fourth-order scalar theory whose mass parameter is determined by $M^2=2H^2$. The Harrison-Zel'dovich scale-invariant spectrum is obtained by Fourier transforming the propagator in position space as well as by computing the power spectrum directly. It shows clearly that the LW scalar theory provides a truly scale-invariant spectrum in whole de Sitter, while the massless scalar propagation in de Sitter shows a scale-invariant spectrum in the superhorizon region only. |
0708.3252 | Alfredo Sandoval-Villalbazo | A. L. Garcia-Perciante, A. Sandoval-Villalbazo, L. S. Garcia-Colin | Generalized Relativistic Chapman-Enskog Solution of the Boltzmann
Equation | 12 pages, no figures | PhysicaA387:5073-5079,2008 | 10.1016/j.physa.2008.05.012 | null | gr-qc | null | The Chapman-Enskog method of solution of the relativistic Boltzmann equation
is generalized in order to admit a time-derivative term associated to a
thermodynamic force in its first order solution. Both existence and uniqueness
of such a solution are proved based on the standard theory of integral
equations. The mathematical implications of the generalization here introduced
are thoroughly discussed regarding the nature of heat as chaotic energy
transfer in the context of relativity theory.
| [
{
"created": "Thu, 23 Aug 2007 21:21:41 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Feb 2008 15:26:03 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Garcia-Perciante",
"A. L.",
""
],
[
"Sandoval-Villalbazo",
"A.",
""
],
[
"Garcia-Colin",
"L. S.",
""
]
] | The Chapman-Enskog method of solution of the relativistic Boltzmann equation is generalized in order to admit a time-derivative term associated to a thermodynamic force in its first order solution. Both existence and uniqueness of such a solution are proved based on the standard theory of integral equations. The mathematical implications of the generalization here introduced are thoroughly discussed regarding the nature of heat as chaotic energy transfer in the context of relativity theory. |
1810.12648 | Ramin Hassannejad | Ramin Hassannejad, S. Navid Mousavi | Deriving Einstein's Field Equation(EFE) and Modified Gravity by
Statistical Mechanics and Quantization of Non-Commuting Space | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we derive the Einstein's field equation (EFE) by considering
an non-commuting two dimensional quantized space, which can be excited by
absorbing energy. Any variation of the energy level of space quantas, will
result in a change in the quanta's area state. This means, that the geometry of
space depends on the energy which exists in it. Using Holographic principle and
Unruh effect, without any further assumptions like equipartition theorem, our
model leads to Newton's law of gravity in the limit $\hbar \to 0$.
| [
{
"created": "Tue, 30 Oct 2018 10:54:40 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Nov 2018 17:23:09 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Jun 2019 09:45:11 GMT",
"version": "v3"
},
{
"created": "Fri, 11 Oct 2019 17:17:33 GMT",
"version": "v4"
},
{
"c... | 2020-01-16 | [
[
"Hassannejad",
"Ramin",
""
],
[
"Mousavi",
"S. Navid",
""
]
] | In this paper, we derive the Einstein's field equation (EFE) by considering an non-commuting two dimensional quantized space, which can be excited by absorbing energy. Any variation of the energy level of space quantas, will result in a change in the quanta's area state. This means, that the geometry of space depends on the energy which exists in it. Using Holographic principle and Unruh effect, without any further assumptions like equipartition theorem, our model leads to Newton's law of gravity in the limit $\hbar \to 0$. |
1910.02081 | Kwinten Fransen | Geoffrey Comp\`ere, Kwinten Fransen, Thomas Hertog and Yan Liu | Scalar Self-force for High Spin Black Holes | 41 pages, 18 figures, published version | Phys. Rev. D 101, 064006 (2020) | 10.1103/PhysRevD.101.064006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We semianalytically investigate the scalar self-force experienced in the
final stages of extreme mass ratio inspirals of nonspinning scalar particles
into supermassive nearly extremal Kerr black holes. We exploit the near-horizon
conformal symmetry to find the self-force for general corotating equatorial
geodesics. The angular component of the self-force is shown to be universal at
leading order in the high spin limit. We verify that the energy and angular
momentum losses of the scalar particle match with the asymptotic fluxes of
scalar radiation. In particular, we relate the previously described persistent
oscillations in the asymptotic energy and angular momentum fluxes with the
local self-force. Such oscillations arise from traveling waves that prevent the
near-horizon and the asymptotic region to fully decouple in the extremal limit.
Conformal invariance is therefore reduced to discrete scale invariance with
associated logarithmic periodicity.
| [
{
"created": "Fri, 4 Oct 2019 18:00:01 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2020 21:23:29 GMT",
"version": "v2"
}
] | 2020-04-07 | [
[
"Compère",
"Geoffrey",
""
],
[
"Fransen",
"Kwinten",
""
],
[
"Hertog",
"Thomas",
""
],
[
"Liu",
"Yan",
""
]
] | We semianalytically investigate the scalar self-force experienced in the final stages of extreme mass ratio inspirals of nonspinning scalar particles into supermassive nearly extremal Kerr black holes. We exploit the near-horizon conformal symmetry to find the self-force for general corotating equatorial geodesics. The angular component of the self-force is shown to be universal at leading order in the high spin limit. We verify that the energy and angular momentum losses of the scalar particle match with the asymptotic fluxes of scalar radiation. In particular, we relate the previously described persistent oscillations in the asymptotic energy and angular momentum fluxes with the local self-force. Such oscillations arise from traveling waves that prevent the near-horizon and the asymptotic region to fully decouple in the extremal limit. Conformal invariance is therefore reduced to discrete scale invariance with associated logarithmic periodicity. |
1208.3589 | Brien C. Nolan | Brien C. Nolan and Elizabeth Winstanley | On the existence of dyons and dyonic black holes in Einstein-Yang-Mills
theory | 23 pages, 2 figures. Minor revisions; references added | null | 10.1088/0264-9381/29/23/235024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study dyonic soliton and black hole solutions of the ${\mathfrak {su}}(2)$
Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove
the existence of non-trivial dyonic soliton and black hole solutions in a
neighbourhood of the trivial solution. For these solutions the magnetic gauge
field function has no zeros and we conjecture that at least some of these
non-trivial solutions will be stable. The global existence proof uses local
existence results and a non-linear perturbation argument based on the (Banach
space) implicit function theorem.
| [
{
"created": "Fri, 17 Aug 2012 13:01:49 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Oct 2012 13:26:28 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Nolan",
"Brien C.",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] | We study dyonic soliton and black hole solutions of the ${\mathfrak {su}}(2)$ Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove the existence of non-trivial dyonic soliton and black hole solutions in a neighbourhood of the trivial solution. For these solutions the magnetic gauge field function has no zeros and we conjecture that at least some of these non-trivial solutions will be stable. The global existence proof uses local existence results and a non-linear perturbation argument based on the (Banach space) implicit function theorem. |
1607.08607 | Ruth Gregory | Anne-Christine Davis, Ruth Gregory and Rahul Jha | Black hole accretion discs and screened scalar hair | 19 pages, 5 figures | null | 10.1088/1475-7516/2016/10/024 | DCPT-16/25 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel way to investigate scalar field profiles around black
holes with an accretion disc for a range of models where the Compton wavelength
of the scalar is large compared to other length scales. By analysing the
problem in "Weyl" coordinates, we are able to calculate the scalar profiles for
accretion discs in the static Schwarzschild, as well as rotating Kerr, black
holes. We comment on observational effects.
| [
{
"created": "Thu, 28 Jul 2016 06:38:29 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Aug 2016 18:55:51 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Davis",
"Anne-Christine",
""
],
[
"Gregory",
"Ruth",
""
],
[
"Jha",
"Rahul",
""
]
] | We present a novel way to investigate scalar field profiles around black holes with an accretion disc for a range of models where the Compton wavelength of the scalar is large compared to other length scales. By analysing the problem in "Weyl" coordinates, we are able to calculate the scalar profiles for accretion discs in the static Schwarzschild, as well as rotating Kerr, black holes. We comment on observational effects. |
2312.16295 | Ding Ding | Ding Ding, Zhao Yu, Yidun Wan | Effective dynamics of quantum fluctuations in field theory: with
applications to cosmology | Typos corrected and clarifications added. Matches the JHEP version | JHEP 04 (2024) 086 | 10.1007/JHEP04(2024)086 | null | gr-qc astro-ph.CO hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We develop a novel framework for describing quantum fluctuations in field
theory, with a focus on cosmological applications. Our method uniquely
circumvents the use of operator/Hilbert-space formalism, instead relying on a
systematic treatment of classical variables, quantum fluctuations, and an
effective Hamiltonian. Our framework not only aligns with standard formalisms
in flat and de Sitter spacetimes, which assumes no backreaction, demonstrated
through the $\varphi^3$-model, but also adeptly handles time-dependent
backreaction in more general cases. The uncertainty principle and spatial
symmetry emerge as critical tools for selecting initial conditions and
understanding effective potentials. We discover that modes inside the Hubble
horizon \emph{do not} necessarily feel an initial Minkowski vacuum, as is
commonly assumed. Our findings offer fresh insights into the early universe's
quantum fluctuations and potential explanations to large-scale CMB anomalies.
| [
{
"created": "Tue, 26 Dec 2023 19:01:24 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Apr 2024 10:35:38 GMT",
"version": "v2"
}
] | 2024-06-25 | [
[
"Ding",
"Ding",
""
],
[
"Yu",
"Zhao",
""
],
[
"Wan",
"Yidun",
""
]
] | We develop a novel framework for describing quantum fluctuations in field theory, with a focus on cosmological applications. Our method uniquely circumvents the use of operator/Hilbert-space formalism, instead relying on a systematic treatment of classical variables, quantum fluctuations, and an effective Hamiltonian. Our framework not only aligns with standard formalisms in flat and de Sitter spacetimes, which assumes no backreaction, demonstrated through the $\varphi^3$-model, but also adeptly handles time-dependent backreaction in more general cases. The uncertainty principle and spatial symmetry emerge as critical tools for selecting initial conditions and understanding effective potentials. We discover that modes inside the Hubble horizon \emph{do not} necessarily feel an initial Minkowski vacuum, as is commonly assumed. Our findings offer fresh insights into the early universe's quantum fluctuations and potential explanations to large-scale CMB anomalies. |
1804.03992 | Pierre-Andr\'e Mandrin Ph.D. | Pierre A Mandrin | Multi-layer statistical gravity on the boundary | 9 pages. Published | Proceedings of the 8th international workshop DICE2016: spacetime
- matter - quantum mechanics, J. Phys.: Conf. Ser. 880 (2016) 012028 | 10.1088/1742-6596/880/1/012028 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from an important research path, we consider gravity as a collective
phenomenon governed by statistical mechanics. While previous studies have
focussed on the thermodynamic heat flow across a 2d-horizon as perceived by a
single, accelerated observer, we evaluate here the number of microscopic states
arising for multiple observers perceiving multiple horizons within foliations
of the boundary of a space-time region. This yields a temperature-independent,
Boltzmann-type "entropy" which is equivalent to the boundary action and which
we call m-entropy. According to its statistical interpretation, the m-entropy
distribution as a function of the gravitational field is maximum when
Einstein's Field Equations hold. However, if the number of "atoms of space" is
small, Einstein's Equations do not hold and no sharp geometry can be defined.
On the other hand, the transition probability of microstates can be computed
and can be interpreted as processes of a (alternative) model of quantum
space-time.
| [
{
"created": "Sat, 7 Apr 2018 15:00:00 GMT",
"version": "v1"
}
] | 2018-04-12 | [
[
"Mandrin",
"Pierre A",
""
]
] | Starting from an important research path, we consider gravity as a collective phenomenon governed by statistical mechanics. While previous studies have focussed on the thermodynamic heat flow across a 2d-horizon as perceived by a single, accelerated observer, we evaluate here the number of microscopic states arising for multiple observers perceiving multiple horizons within foliations of the boundary of a space-time region. This yields a temperature-independent, Boltzmann-type "entropy" which is equivalent to the boundary action and which we call m-entropy. According to its statistical interpretation, the m-entropy distribution as a function of the gravitational field is maximum when Einstein's Field Equations hold. However, if the number of "atoms of space" is small, Einstein's Equations do not hold and no sharp geometry can be defined. On the other hand, the transition probability of microstates can be computed and can be interpreted as processes of a (alternative) model of quantum space-time. |
2201.00633 | Mohammad Atazadeh | M. Mousavi, K. Atazadeh | Cosmological future singularities in massive gravity and massive
bigravity | 14 pages, 8(*6) figures, references added | Physics of the Dark Universe 35 (2022) 100942 | 10.1016/j.dark.2021.100942 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the future cosmological singularities in the framework of massive
gravity and minimal massive bigravity theory. In this regards, we consider the
possible classes of finite-time future singularities such as sudden, big rip,
big freeze and big brake singularities in the massive universe. In dRGT model
with an open expanding universe we obtain the sudden singularity in the future
at a finite-time which generally without taking account of any particular
realistic equation of state, is not avoidable and except the fluid density, all
dynamical physical quantities such as pressure approach to infinity. To
complete our study, we search the future cosmological singularities in the
context of minimal massive bigravity theory and we find that the cosmology of
this theory suffers from the sudden and big brake singularities, in which we
can see that the parameters of the model approaches to zero the sudden
singularity can be removed.
| [
{
"created": "Mon, 3 Jan 2022 13:12:30 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jan 2022 16:02:03 GMT",
"version": "v2"
}
] | 2022-01-27 | [
[
"Mousavi",
"M.",
""
],
[
"Atazadeh",
"K.",
""
]
] | We study the future cosmological singularities in the framework of massive gravity and minimal massive bigravity theory. In this regards, we consider the possible classes of finite-time future singularities such as sudden, big rip, big freeze and big brake singularities in the massive universe. In dRGT model with an open expanding universe we obtain the sudden singularity in the future at a finite-time which generally without taking account of any particular realistic equation of state, is not avoidable and except the fluid density, all dynamical physical quantities such as pressure approach to infinity. To complete our study, we search the future cosmological singularities in the context of minimal massive bigravity theory and we find that the cosmology of this theory suffers from the sudden and big brake singularities, in which we can see that the parameters of the model approaches to zero the sudden singularity can be removed. |
2101.11129 | Huan Yang | Huan Yang | Relating Black Hole Shadow to Quasinormal Modes for Rotating Black Holes | 7 pages, 3 figures | Phys. Rev. D 103, 084010 (2021) | 10.1103/PhysRevD.103.084010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we explore the connection between the critical curves
("shadows") and the quasinormal mode frequencies (in the eikonal limit) of Kerr
black holes. This mapping has been previously established for non-rotating
black holes. We show that, the shadow seen by an distant observer at a given
inclination angle, can be mapped to a family of quasinormal modes with
$m/(\ell+1/2)$ bounded within certain range, where $m$ is is azimuthal node
number and $\ell$ is the angular node number. We discuss the possibility of
testing such relation with space-borne gravitational wave detectors and the
next-generation Event Horizon Telescope.
| [
{
"created": "Tue, 26 Jan 2021 23:11:57 GMT",
"version": "v1"
}
] | 2021-04-14 | [
[
"Yang",
"Huan",
""
]
] | In this work, we explore the connection between the critical curves ("shadows") and the quasinormal mode frequencies (in the eikonal limit) of Kerr black holes. This mapping has been previously established for non-rotating black holes. We show that, the shadow seen by an distant observer at a given inclination angle, can be mapped to a family of quasinormal modes with $m/(\ell+1/2)$ bounded within certain range, where $m$ is is azimuthal node number and $\ell$ is the angular node number. We discuss the possibility of testing such relation with space-borne gravitational wave detectors and the next-generation Event Horizon Telescope. |
gr-qc/9906069 | Bernhard Haisch | Bernhard Haisch and Alfonso Rueda | Progress in Establishing a Connection Between the Electromagnetic
Zero-Point Field and Inertia | 6 pages, no figures | Space Technology and Applications International Forum-99, American
Institute of Physics Conference Proceedings 458, Mohammed S. El-Genk, ed., p.
988 (1999) | 10.1063/1.57490 | null | gr-qc | null | We report on the progress of a NASA-funded study being carried out at the
Lockheed Martin Advanced Technology Center in Palo Alto and the California
State University in Long Beach to investigate the proposed link between the
zero-point field of the quantum vacuum and inertia. It is well known that an
accelerating observer will experience a bath of radiation resulting from the
quantum vacuum which mimics that of a heat bath, the so-called Davies-Unruh
effect. We have further analyzed this problem of an accelerated object moving
through the vacuum and have shown that the zero-point field will yield a
non-zero Poynting vector to an accelerating observer. Scattering of this
radiation by the quarks and electrons constituting matter would result in an
acceleration-dependent reaction force that would appear to be the origin of
inertia of matter (Rueda and Haisch 1998a, 1998b). In the subrelativistic case
this inertia reaction force is exactly newtonian and in the relativistic case
it exactly reproduces the well known relativistic extension of Newton's Law.
This analysis demonstrates then that both the ordinary, F=ma, and the
relativistic forms of Newton's equation of motion may be derived from Maxwell's
equations as applied to the electromagnetic zero-point field. We expect to be
able to extend this analysis in the future to more general versions of the
quantum vacuum than just the electromagnetic one discussed herein.
| [
{
"created": "Wed, 16 Jun 1999 23:33:02 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Haisch",
"Bernhard",
""
],
[
"Rueda",
"Alfonso",
""
]
] | We report on the progress of a NASA-funded study being carried out at the Lockheed Martin Advanced Technology Center in Palo Alto and the California State University in Long Beach to investigate the proposed link between the zero-point field of the quantum vacuum and inertia. It is well known that an accelerating observer will experience a bath of radiation resulting from the quantum vacuum which mimics that of a heat bath, the so-called Davies-Unruh effect. We have further analyzed this problem of an accelerated object moving through the vacuum and have shown that the zero-point field will yield a non-zero Poynting vector to an accelerating observer. Scattering of this radiation by the quarks and electrons constituting matter would result in an acceleration-dependent reaction force that would appear to be the origin of inertia of matter (Rueda and Haisch 1998a, 1998b). In the subrelativistic case this inertia reaction force is exactly newtonian and in the relativistic case it exactly reproduces the well known relativistic extension of Newton's Law. This analysis demonstrates then that both the ordinary, F=ma, and the relativistic forms of Newton's equation of motion may be derived from Maxwell's equations as applied to the electromagnetic zero-point field. We expect to be able to extend this analysis in the future to more general versions of the quantum vacuum than just the electromagnetic one discussed herein. |
0908.3384 | Manuel Hohmann | Manuel Hohmann, Mattias N. R. Wohlfarth | No-go theorem for bimetric gravity with positive and negative mass | 19 pages, no figures, journal version | Phys. Rev. D 80 (2009) 104011 | 10.1103/PhysRevD.80.104011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that the most conservative geometric extension of Einstein gravity
describing both positive and negative mass sources and observers is bimetric
gravity and contains two copies of standard model matter which interact only
gravitationally. Matter fields related to one of the metrics then appear dark
from the point of view of an observer defined by the other metric, and so may
provide a potential explanation for the dark universe. In this framework we
consider the most general form of linearized field equations compatible with
physically and mathematically well-motivated assumptions. Using gauge-invariant
linear perturbation theory, we prove a no-go theorem ruling out all bimetric
gravity theories that, in the Newtonian limit, lead to precisely opposite
forces on positive and negative test masses.
| [
{
"created": "Mon, 24 Aug 2009 09:17:11 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Nov 2009 09:57:00 GMT",
"version": "v2"
}
] | 2009-11-16 | [
[
"Hohmann",
"Manuel",
""
],
[
"Wohlfarth",
"Mattias N. R.",
""
]
] | We argue that the most conservative geometric extension of Einstein gravity describing both positive and negative mass sources and observers is bimetric gravity and contains two copies of standard model matter which interact only gravitationally. Matter fields related to one of the metrics then appear dark from the point of view of an observer defined by the other metric, and so may provide a potential explanation for the dark universe. In this framework we consider the most general form of linearized field equations compatible with physically and mathematically well-motivated assumptions. Using gauge-invariant linear perturbation theory, we prove a no-go theorem ruling out all bimetric gravity theories that, in the Newtonian limit, lead to precisely opposite forces on positive and negative test masses. |
2302.06346 | Serge Parnovsky | S.L. Parnovsky | The dynamics of general Bianchi IX model near the cosmological
singularity | 9 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1202.5448 by other authors | Ukr. J. Phys. Vol. 67 No. 2 P.93-101 (2022) | 10.15407/ujpe67.2.93 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Half a century ago, Belinsky and Khalatnikov proposed a generic solution of
the Einstein equations near their cosmological singularity, based on a
generalization of the homogeneous model of Bianchi type IX. Consideration of
the evolution of the most general non-diagonal case of this model is greatly
simplified if it is assumed that, when approaching the singularity t=0, it
reduces to the so-called asymptotic dynamics, at which inequality (6) holds. It
has been suggested that this inequality continues to be true from the moment of
its first fulfilment up to the singularity of space-time. We analyze this
assumption and show that it is incorrect in the general case. However, it is
shown that there is always a time t_0, after which this assumption becomes
true. The value of t_0 is the smaller the less is the degree of non-diagonality
of the model. Some details of the behaviour of the non-diagonal homogeneous
model of Bianchi type IX are considered at the stage of asymptotic dynamics of
approaching the singularity.
| [
{
"created": "Mon, 13 Feb 2023 13:27:21 GMT",
"version": "v1"
}
] | 2023-02-14 | [
[
"Parnovsky",
"S. L.",
""
]
] | Half a century ago, Belinsky and Khalatnikov proposed a generic solution of the Einstein equations near their cosmological singularity, based on a generalization of the homogeneous model of Bianchi type IX. Consideration of the evolution of the most general non-diagonal case of this model is greatly simplified if it is assumed that, when approaching the singularity t=0, it reduces to the so-called asymptotic dynamics, at which inequality (6) holds. It has been suggested that this inequality continues to be true from the moment of its first fulfilment up to the singularity of space-time. We analyze this assumption and show that it is incorrect in the general case. However, it is shown that there is always a time t_0, after which this assumption becomes true. The value of t_0 is the smaller the less is the degree of non-diagonality of the model. Some details of the behaviour of the non-diagonal homogeneous model of Bianchi type IX are considered at the stage of asymptotic dynamics of approaching the singularity. |
1312.6355 | Marek Czachor | Marek Czachor, Andrzej Posiewnik | Wavepacket of the Universe and its spreading | v1 preliminary report, v2 includes sections on the explicit form of
the evolution operator, v3 includes an explicit analysis based on
Kolmogorov-Nagumo-Renyi averaging, v4 section on 1+3 generalization is
corrected, v5 conflict of notation in Bernoulli and Renyi forms is fixed; v6
accepted in Int.J.Theor.Phys | Int. J. Theor. Phys. 55, 2001-2011 (2016) | 10.1007/s10773-015-2840-7 | null | gr-qc nlin.CD quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wavepackets in quantum mechanics spread and the Universe in cosmology
expands. We discuss a formalism where the two effects can be unified. The basic
assumption is that the Universe is determined by a unitarily evolving
wavepacket defined on space-time. Space-time is static but the Universe is
dynamic. Spreading analogous to expansion known from observational cosmology is
obtained if one regards time evolution as a discrete process with probabilities
of jumps determined by a variational principle employing
Kolmogorov-Nagumo-R\'enyi averages. The choice of the R\'enyi calculus implies
that the form of the Universe involves an implicit fractal structure. The
formalism automatically leads to two types of "time" parameters: $\tau$, with
dimension of $x^0$, and dimensionless $\varepsilon=\ln \epsilon_\tau$, related
to the form of diffeomorphism that defines the dynamics. There is no preferred
time foliation, but effectively the dynamics leads to asymptotic concentration
of the Universe on spacelike surfaces that propagate in space-time. The
analysis is performed explicitly in $1+1$ dimensions, but the unitary evolution
operator is brought to a form that makes generalizations to other dimensions
and other fields quite natural.
| [
{
"created": "Sun, 22 Dec 2013 09:53:09 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jan 2014 16:09:15 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Apr 2014 12:12:08 GMT",
"version": "v3"
},
{
"created": "Sun, 11 May 2014 09:48:09 GMT",
"version": "v4"
},
{
"cr... | 2016-04-22 | [
[
"Czachor",
"Marek",
""
],
[
"Posiewnik",
"Andrzej",
""
]
] | Wavepackets in quantum mechanics spread and the Universe in cosmology expands. We discuss a formalism where the two effects can be unified. The basic assumption is that the Universe is determined by a unitarily evolving wavepacket defined on space-time. Space-time is static but the Universe is dynamic. Spreading analogous to expansion known from observational cosmology is obtained if one regards time evolution as a discrete process with probabilities of jumps determined by a variational principle employing Kolmogorov-Nagumo-R\'enyi averages. The choice of the R\'enyi calculus implies that the form of the Universe involves an implicit fractal structure. The formalism automatically leads to two types of "time" parameters: $\tau$, with dimension of $x^0$, and dimensionless $\varepsilon=\ln \epsilon_\tau$, related to the form of diffeomorphism that defines the dynamics. There is no preferred time foliation, but effectively the dynamics leads to asymptotic concentration of the Universe on spacelike surfaces that propagate in space-time. The analysis is performed explicitly in $1+1$ dimensions, but the unitary evolution operator is brought to a form that makes generalizations to other dimensions and other fields quite natural. |
0901.4009 | Joseph Henson | Joe Henson | Quantum Histories and Quantum Gravity | 35 pages (29 pages main body), two figures | J.Phys.Conf.Ser.174:012020,2009 | 10.1088/1742-6596/174/1/012020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper reviews the histories approach to quantum mechanics. This
discussion is then applied to theories of quantum gravity. It is argued that
some of the quantum histories must approximate (in a suitable sense) to
classical histories, if the correct classical regime is to be recovered. This
observation has significance for the formulation of new theories (such as
quantum gravity theories) as it puts a constraint on the kinematics, if the
quantum/classical correspondence principle is to be preserved. Consequences for
quantum gravity, particularly for Lorentz symmetry and the idea of "emergent
geometry", are discussed.
| [
{
"created": "Mon, 26 Jan 2009 14:13:18 GMT",
"version": "v1"
}
] | 2009-07-24 | [
[
"Henson",
"Joe",
""
]
] | This paper reviews the histories approach to quantum mechanics. This discussion is then applied to theories of quantum gravity. It is argued that some of the quantum histories must approximate (in a suitable sense) to classical histories, if the correct classical regime is to be recovered. This observation has significance for the formulation of new theories (such as quantum gravity theories) as it puts a constraint on the kinematics, if the quantum/classical correspondence principle is to be preserved. Consequences for quantum gravity, particularly for Lorentz symmetry and the idea of "emergent geometry", are discussed. |
2311.12907 | Mikhail Katanaev | M. O. Katanaev | Complete separation of variables in the geodesic Hamilton--Jacobi
equation in four dimensions | 11 pages. arXiv admin note: substantial text overlap with
arXiv:2305.02222 | Phys. Scr. 98 (2023)104001 | 10.1088/1402-4896/acf251 | null | gr-qc math-ph math.MP | http://creativecommons.org/publicdomain/zero/1.0/ | We list all metrics of arbitrary signature in four dimensions which admit
complete separation of variables in the Hamilton--Jacobi equation for geodesic
Hamiltonians. There are only ten classes of separable metrics admitting
commuting Killing vector fields, indecomposable quadratic conservation laws,
and coisotropic coordinates. Canonical separable metrics parameterized by
several (up to twelve) arbitrary functions of single coordinates are written
explicitly. The full set of independent conservation laws in involution for
each canonical metrics is also found.
| [
{
"created": "Tue, 21 Nov 2023 13:55:06 GMT",
"version": "v1"
}
] | 2023-11-23 | [
[
"Katanaev",
"M. O.",
""
]
] | We list all metrics of arbitrary signature in four dimensions which admit complete separation of variables in the Hamilton--Jacobi equation for geodesic Hamiltonians. There are only ten classes of separable metrics admitting commuting Killing vector fields, indecomposable quadratic conservation laws, and coisotropic coordinates. Canonical separable metrics parameterized by several (up to twelve) arbitrary functions of single coordinates are written explicitly. The full set of independent conservation laws in involution for each canonical metrics is also found. |
1303.4516 | Claes Uggla | Claes Uggla, John Wainwright | Asymptotic analysis of perturbed dust cosmologies to second order | 23 pages, no figures | Gen. Rel. Grav. 45 (2013) 1467 | 10.1007/s10714-013-1559-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a
positive cosmological constant have recently attracted considerable attention.
In this paper our first goal is to compare the evolution of the first and
second order perturbations by determining their asymptotic behaviour at late
times in ever-expanding models. We show that in the presence of spatial
curvature K or a positive cosmological constant, the density perturbation
approaches a finite limit both to first and second order, but the rate of
approach depends on the model, being power law in the scale factor if the
cosmological constant is positive but logarithmic if it is zero and and K<0.
Scalar perturbations in general contain a growing and a decaying mode. We find,
somewhat surprisingly, that if the cosmological constant is positive the
decaying mode does not die away, i.e. it contributes on an equal footing as the
growing mode to the asymptotic expression for the density perturbation. On the
other hand, the future asymptotic regime of the Einstein-de Sitter universe
(for which the cosmological constant and the spatial curvature are both zero)
is completely different, as exemplified by the density perturbation which
diverges; moreover, the second order perturbation diverges faster than the
first order perturbation, which suggests that the Einstein-de Sitter universe
is unstable to perturbations, and that the perturbation series do not converge
towards the future. We conclude that the presence of spatial curvature or a
cosmological constant stabilizes the perturbations. Our second goal is to
derive an explicit expression for the second order density perturbation that
can be used to study the effects of including a cosmological constant and
spatial curvature.
| [
{
"created": "Tue, 19 Mar 2013 09:10:39 GMT",
"version": "v1"
}
] | 2013-08-28 | [
[
"Uggla",
"Claes",
""
],
[
"Wainwright",
"John",
""
]
] | Nonlinear perturbations of Friedmann-Lemaitre cosmologies with dust and a positive cosmological constant have recently attracted considerable attention. In this paper our first goal is to compare the evolution of the first and second order perturbations by determining their asymptotic behaviour at late times in ever-expanding models. We show that in the presence of spatial curvature K or a positive cosmological constant, the density perturbation approaches a finite limit both to first and second order, but the rate of approach depends on the model, being power law in the scale factor if the cosmological constant is positive but logarithmic if it is zero and and K<0. Scalar perturbations in general contain a growing and a decaying mode. We find, somewhat surprisingly, that if the cosmological constant is positive the decaying mode does not die away, i.e. it contributes on an equal footing as the growing mode to the asymptotic expression for the density perturbation. On the other hand, the future asymptotic regime of the Einstein-de Sitter universe (for which the cosmological constant and the spatial curvature are both zero) is completely different, as exemplified by the density perturbation which diverges; moreover, the second order perturbation diverges faster than the first order perturbation, which suggests that the Einstein-de Sitter universe is unstable to perturbations, and that the perturbation series do not converge towards the future. We conclude that the presence of spatial curvature or a cosmological constant stabilizes the perturbations. Our second goal is to derive an explicit expression for the second order density perturbation that can be used to study the effects of including a cosmological constant and spatial curvature. |
1505.07770 | Ikjyot Singh Kohli | Ikjyot Singh Kohli | On Singularities in Cosmic Inflation | Added some references, updated some equations | null | null | null | gr-qc astro-ph.CO math-ph math.CA math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine a flat FLRW spacetime with a scalar field potential
and show by applying Osgood's criterion to the Einstein field equations that
all such models, irrespective of the particular choice of potential develop
finite-time singularities. That is, we show that solutions to the field
equations become singular in finite time, which can have important implications
for the role of inflation in cosmological models. We further point out that a
possible reason for this behaviour is that the solutions to the field equations
in such inflationary scenarios do not obey global existence and uniqueness
properties, which is a typical characteristic of solutions that diverge in
finite time.
| [
{
"created": "Thu, 28 May 2015 17:39:32 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2015 15:16:43 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Jul 2015 16:39:30 GMT",
"version": "v3"
},
{
"created": "Mon, 25 Apr 2016 15:19:32 GMT",
"version": "v4"
}
] | 2016-04-26 | [
[
"Kohli",
"Ikjyot Singh",
""
]
] | In this paper, we examine a flat FLRW spacetime with a scalar field potential and show by applying Osgood's criterion to the Einstein field equations that all such models, irrespective of the particular choice of potential develop finite-time singularities. That is, we show that solutions to the field equations become singular in finite time, which can have important implications for the role of inflation in cosmological models. We further point out that a possible reason for this behaviour is that the solutions to the field equations in such inflationary scenarios do not obey global existence and uniqueness properties, which is a typical characteristic of solutions that diverge in finite time. |
2011.10503 | Oliver Fabio Piattella | J\'ulio C. Fabris, Oliver F. Piattella, and Davi C. Rodrigues | On Rastall gravity formulation as a $f(R,\mathcal{L}_m)$ and a $f(R,T)$
theory | 11 pages, accepted for publication in the European Physical Journal
Plus | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rastall introduced a stress-energy tensor whose divergence is proportional to
the gradient of the Ricci scalar. This proposal leads to a change in the form
of the field equations of General Relativity, but it preserves the number of
degrees of freedom. Rastall's field equations can be either interpreted as GR
with a redefined SET, or it can imply different physical consequences inside
the matter sector. We investigate limits under which the Rastall field
equations can be directly derived from an action, in particular from two
$f(R)$-gravity extensions: $f(R,\mathcal L_m)$ and $f(R,T)$. We show that there
are similarities between these theories, but the Rastall SET cannot be fully
recovered from them, apart from certain particular cases here discussed. It is
remarkable that a simple, covariant and invertible redefinition of the SET, as
the one proposed by Rastall, is hard to be directly implemented in the action.
| [
{
"created": "Fri, 20 Nov 2020 17:03:48 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Nov 2022 09:18:01 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Feb 2023 14:43:41 GMT",
"version": "v3"
}
] | 2023-02-28 | [
[
"Fabris",
"Júlio C.",
""
],
[
"Piattella",
"Oliver F.",
""
],
[
"Rodrigues",
"Davi C.",
""
]
] | Rastall introduced a stress-energy tensor whose divergence is proportional to the gradient of the Ricci scalar. This proposal leads to a change in the form of the field equations of General Relativity, but it preserves the number of degrees of freedom. Rastall's field equations can be either interpreted as GR with a redefined SET, or it can imply different physical consequences inside the matter sector. We investigate limits under which the Rastall field equations can be directly derived from an action, in particular from two $f(R)$-gravity extensions: $f(R,\mathcal L_m)$ and $f(R,T)$. We show that there are similarities between these theories, but the Rastall SET cannot be fully recovered from them, apart from certain particular cases here discussed. It is remarkable that a simple, covariant and invertible redefinition of the SET, as the one proposed by Rastall, is hard to be directly implemented in the action. |
1609.09779 | Sunandan Gangopadhyay | Saumya Ghosh, Sunandan Gangopadhyay | Thermodynamics and emergent universe | 10 pages Latex | Mod. Phys. Lett. A 32 (2017) 1750089 | 10.1142/S0217732317500894 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that in the isentropic scenario the first order thermodynamical
particle creation model gives an emergent universe solution even when the
chemical potential is non-zero. However there exists no emergent universe
scenario in the second order non-equilibrium theory for the particle creation
model. We then point out a correspondence between the particle creation model
with barotropic equation of state and the equation of state giving rise to an
emergent universe without particle creation in spatially flat FRW cosmology.
| [
{
"created": "Wed, 28 Sep 2016 15:05:31 GMT",
"version": "v1"
}
] | 2017-05-01 | [
[
"Ghosh",
"Saumya",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | We show that in the isentropic scenario the first order thermodynamical particle creation model gives an emergent universe solution even when the chemical potential is non-zero. However there exists no emergent universe scenario in the second order non-equilibrium theory for the particle creation model. We then point out a correspondence between the particle creation model with barotropic equation of state and the equation of state giving rise to an emergent universe without particle creation in spatially flat FRW cosmology. |
2110.14630 | Ruslan Muharlyamov | Ruslan K. Muharlyamov, Tatiana N. Pankratyeva | The nonlinear anisotropic model of the Universe with the linear
potential | null | Indian J Phys (2022) | 10.1007/s12648-022-02556-0 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the Bianchi I cosmology some subclasses of the Horndeski theory allow for
the non-standard anisotropy behavior. For example, the anisotropy is damped
near the initial singularity instead of tending to infinity. In this article,
we analyze the nonlinear anisotropic model with the linear potential.We have
considered an example of such theory, for which the anisotropy is always
finite. The anisotropy reaches its a maximum value at the initial moment. The
anisotropy suppression occurs during the inflationary stage, and it approaches
zero at later times. This cosmological model does not contain the singular
point.
| [
{
"created": "Wed, 27 Oct 2021 17:55:45 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Dec 2022 11:25:41 GMT",
"version": "v2"
}
] | 2022-12-27 | [
[
"Muharlyamov",
"Ruslan K.",
""
],
[
"Pankratyeva",
"Tatiana N.",
""
]
] | In the Bianchi I cosmology some subclasses of the Horndeski theory allow for the non-standard anisotropy behavior. For example, the anisotropy is damped near the initial singularity instead of tending to infinity. In this article, we analyze the nonlinear anisotropic model with the linear potential.We have considered an example of such theory, for which the anisotropy is always finite. The anisotropy reaches its a maximum value at the initial moment. The anisotropy suppression occurs during the inflationary stage, and it approaches zero at later times. This cosmological model does not contain the singular point. |
gr-qc/0106092 | Andrey Neronov | Andrey Neronov | Fermion masses and quantum numbers from extra dimensions | 14 pages | Phys.Rev.D65:044004,2002 | 10.1103/PhysRevD.65.044004 | null | gr-qc hep-ph hep-th | null | We study the localization of fermions on a brane embedded in a space-time
with $AdS_n \times M^k$ geometry. Quantum numbers of localized fermions are
associated with their rotation momenta around the brane. Fermions with
different quantum numbers have different higher-dimensional profiles. Fermion
masses and mixings, which are proportional to the overlap of higher-dimensional
profiles of the fermions, depend on the fermion quantum numbers.
| [
{
"created": "Thu, 28 Jun 2001 19:08:17 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Neronov",
"Andrey",
""
]
] | We study the localization of fermions on a brane embedded in a space-time with $AdS_n \times M^k$ geometry. Quantum numbers of localized fermions are associated with their rotation momenta around the brane. Fermions with different quantum numbers have different higher-dimensional profiles. Fermion masses and mixings, which are proportional to the overlap of higher-dimensional profiles of the fermions, depend on the fermion quantum numbers. |
1901.08804 | Pratyusava Baral | Pratyusava Baral, Anarya Ray, Ratna Koley and Parthasarathi Majumdar | Gravitational Waves with Orbital Angular Momentum | 8 pages, 4 figures Version to appear in EPJC | null | 10.1140/epjc/s10052-020-7881-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compact orbiting binaries like the black hole binary system observed in
GW150914 carry large amount of orbital angular momentum. The post-ringdown
compact object formed after merger of such a binary configuration has only spin
angular momentum, and this results in a large orbital angular momentum excess.
One significant possibility is that the gravitational waves generated by the
system carry away this excess orbital angular momentum. An estimate of this
excess is made. Arguing that plane gravitational waves cannot possibly carry
any orbital angular momentum, a case is made in this paper for gravitational
wave beams carrying orbital angular momentum, akin to optical beams.
Restricting to certain specific beam-configurations, we predict that such beams
may produce a new type of strain, in addition to the longitudinal strains
measured at aLIGO for GW150914 and GW170817. Current constraints on
post-ringdown spins, derived within the planewave approximation of
gravitational waves, therefore stand to improve. The minimal modification that
might be needed on a laser-interferometer detector (like aLIGO or VIRGO) to
detect such additional strains is also briefly discussed.
| [
{
"created": "Fri, 25 Jan 2019 09:58:35 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Mar 2019 06:55:13 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Mar 2020 18:01:23 GMT",
"version": "v3"
}
] | 2020-05-20 | [
[
"Baral",
"Pratyusava",
""
],
[
"Ray",
"Anarya",
""
],
[
"Koley",
"Ratna",
""
],
[
"Majumdar",
"Parthasarathi",
""
]
] | Compact orbiting binaries like the black hole binary system observed in GW150914 carry large amount of orbital angular momentum. The post-ringdown compact object formed after merger of such a binary configuration has only spin angular momentum, and this results in a large orbital angular momentum excess. One significant possibility is that the gravitational waves generated by the system carry away this excess orbital angular momentum. An estimate of this excess is made. Arguing that plane gravitational waves cannot possibly carry any orbital angular momentum, a case is made in this paper for gravitational wave beams carrying orbital angular momentum, akin to optical beams. Restricting to certain specific beam-configurations, we predict that such beams may produce a new type of strain, in addition to the longitudinal strains measured at aLIGO for GW150914 and GW170817. Current constraints on post-ringdown spins, derived within the planewave approximation of gravitational waves, therefore stand to improve. The minimal modification that might be needed on a laser-interferometer detector (like aLIGO or VIRGO) to detect such additional strains is also briefly discussed. |
gr-qc/9302027 | Ranjeet S. Tate | Abhay Ashtekar, Ranjeet S. Tate and Claes Uggla | Minisuperspaces: Observables and Quantization | 34 pages | Int.J.Mod.Phys.D2:15-50,1993 | 10.1142/S0218271893000039 | Syracuse University preprint SU-GP-92/2-6 | gr-qc | null | A canonical transformation is performed on the phase space of a number of
homogeneous cosmologies to simplify the form of the scalar (or, Hamiltonian)
constraint. Using the new canonical coordinates, it is then easy to obtain
explicit expressions of Dirac observables, i.e.\ phase space functions which
commute weakly with the constraint. This, in turn, enables us to carry out a
general quantization program to completion. We are also able to address the
issue of time through ``deparametrization'' and discuss physical questions such
as the fate of initial singularities in the quantum theory. We find that they
persist in the quantum theory {\it inspite of the fact that the evolution is
implemented by a 1-parameter family of unitary transformations}. Finally,
certain of these models admit conditional symmetries which are explicit already
prior to the canonical transformation. These can be used to pass to quantum
theory following an independent avenue. The two quantum theories --based,
respectively, on Dirac observables in the new canonical variables and
conditional symmetries in the original ADM variables-- are compared and shown
to be equivalent.
| [
{
"created": "Sun, 21 Feb 1993 07:47:45 GMT",
"version": "v1"
}
] | 2009-07-10 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Tate",
"Ranjeet S.",
""
],
[
"Uggla",
"Claes",
""
]
] | A canonical transformation is performed on the phase space of a number of homogeneous cosmologies to simplify the form of the scalar (or, Hamiltonian) constraint. Using the new canonical coordinates, it is then easy to obtain explicit expressions of Dirac observables, i.e.\ phase space functions which commute weakly with the constraint. This, in turn, enables us to carry out a general quantization program to completion. We are also able to address the issue of time through ``deparametrization'' and discuss physical questions such as the fate of initial singularities in the quantum theory. We find that they persist in the quantum theory {\it inspite of the fact that the evolution is implemented by a 1-parameter family of unitary transformations}. Finally, certain of these models admit conditional symmetries which are explicit already prior to the canonical transformation. These can be used to pass to quantum theory following an independent avenue. The two quantum theories --based, respectively, on Dirac observables in the new canonical variables and conditional symmetries in the original ADM variables-- are compared and shown to be equivalent. |
1503.05109 | Sunil Kumar Tripathy Dr. | S. K. Tripathy, B. Mishra and P. K. Sahoo | Two fluid anisotropic dark energy models in a scale invariant theory | 20 pages, 10 figures, accepted for publication in Eur. Phys. J. Plus | Eur. Phys. J. Plus, 132:388, 2017 | 10.1140/epjp/i2017-11672-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some anisotropic Bianchi V dark energy models are investigated in a scale
invariant theory of gravity. We consider two non interacting fluids such as
dark energy and a bulk viscous fluid. Dark energy pressure is considered to be
anisotropic in different spatial directions. A dynamically evolving pressure
anisotropy is obtained from the models. The models favour phantom behaviour. It
is observed that, in presence of dark energy, bulk viscosity has no appreciable
affect on the cosmic dynamics.
| [
{
"created": "Sun, 15 Mar 2015 05:59:12 GMT",
"version": "v1"
},
{
"created": "Mon, 29 May 2017 18:03:26 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Aug 2017 15:59:23 GMT",
"version": "v3"
}
] | 2017-10-25 | [
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Some anisotropic Bianchi V dark energy models are investigated in a scale invariant theory of gravity. We consider two non interacting fluids such as dark energy and a bulk viscous fluid. Dark energy pressure is considered to be anisotropic in different spatial directions. A dynamically evolving pressure anisotropy is obtained from the models. The models favour phantom behaviour. It is observed that, in presence of dark energy, bulk viscosity has no appreciable affect on the cosmic dynamics. |
1907.07497 | Isha Kotecha | Isha Kotecha | Thermal quantum spacetime | v2 minor changes, published version; 19 pages, 1 figure; invited
contribution to the special issue "Progress in Group Field Theory and Related
Quantum Gravity Formalisms", eds. S. Carrozza, S. Gielen and D. Oriti | null | 10.3390/universe5080187 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The intersection of thermodynamics, quantum theory and gravity has revealed
many profound insights, all the while posing new puzzles. In this article, we
discuss an extension of equilibrium statistical mechanics and thermodynamics
potentially compatible with a key feature of general relativity, background
independence; and we subsequently use it in a candidate quantum gravity system,
thus providing a preliminary formulation of a thermal quantum spacetime.
Specifically, we emphasise on an information-theoretic characterisation of
generalised Gibbs equilibrium that is shown to be particularly suited to
background independent settings, and in which the status of entropy is elevated
to being more fundamental than energy. We also shed light on its intimate
connections with the thermal time hypothesis. Based on this we outline a
framework for statistical mechanics of quantum gravity degrees of freedom of
combinatorial and algebraic type, and apply it in several examples. In
particular, we provide a quantum statistical basis for the origin of covariant
group field theories, shown to arise as effective statistical field theories of
the underlying quanta of space in a certain class of generalised Gibbs states.
| [
{
"created": "Wed, 17 Jul 2019 13:18:21 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2019 17:06:23 GMT",
"version": "v2"
}
] | 2019-08-13 | [
[
"Kotecha",
"Isha",
""
]
] | The intersection of thermodynamics, quantum theory and gravity has revealed many profound insights, all the while posing new puzzles. In this article, we discuss an extension of equilibrium statistical mechanics and thermodynamics potentially compatible with a key feature of general relativity, background independence; and we subsequently use it in a candidate quantum gravity system, thus providing a preliminary formulation of a thermal quantum spacetime. Specifically, we emphasise on an information-theoretic characterisation of generalised Gibbs equilibrium that is shown to be particularly suited to background independent settings, and in which the status of entropy is elevated to being more fundamental than energy. We also shed light on its intimate connections with the thermal time hypothesis. Based on this we outline a framework for statistical mechanics of quantum gravity degrees of freedom of combinatorial and algebraic type, and apply it in several examples. In particular, we provide a quantum statistical basis for the origin of covariant group field theories, shown to arise as effective statistical field theories of the underlying quanta of space in a certain class of generalised Gibbs states. |
gr-qc/9611054 | Miguel Navarro | J. Cruz, J. Navarro-Salas, M. Navarro and C. F. Talavera | New Symmetries in Two-Dimensional Dilaton Gravity | Talk given at the XXI International Colloquium on Group Theoretical
Methods in Physics. 15--20 July 1996, Goslar, Germany. To appear in the
Proceedings. 6 pages | null | null | null | gr-qc | null | We present three types of non-conformal symmetries for a wide class of 2D
dilaton-gravity models. For the particular CGHS, or string-inspired model, a
linear combination of these symmetries is conformal and turns out to be the
well-known symmetry which allows to construct the exactly solvable
semiclassical RST and BPP models. We show that one of these non-conformal
symmetries can be converted into a conformal one by means of a suitable field
redefinition involving the metric and the derivatives of the dilaton. As a
consequence of this, and by defining a Polyakov-type term in terms of an
invariant metric under the symmetry, we are able to provide, for a generic 2D
dilaton gravity model, associated semiclassical models which are symmetry
invariant.
| [
{
"created": "Fri, 22 Nov 1996 11:39:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cruz",
"J.",
""
],
[
"Navarro-Salas",
"J.",
""
],
[
"Navarro",
"M.",
""
],
[
"Talavera",
"C. F.",
""
]
] | We present three types of non-conformal symmetries for a wide class of 2D dilaton-gravity models. For the particular CGHS, or string-inspired model, a linear combination of these symmetries is conformal and turns out to be the well-known symmetry which allows to construct the exactly solvable semiclassical RST and BPP models. We show that one of these non-conformal symmetries can be converted into a conformal one by means of a suitable field redefinition involving the metric and the derivatives of the dilaton. As a consequence of this, and by defining a Polyakov-type term in terms of an invariant metric under the symmetry, we are able to provide, for a generic 2D dilaton gravity model, associated semiclassical models which are symmetry invariant. |
2106.06821 | Ivan de Martino | Ivan de Martino, Riccardo della Monica, Mariafelicia de Laurentis | $f(R)$-gravity after the detection of the orbital precession of the S2
star around the Galactic centre massive black hole | 8 pages, 1 Figure, and Supplemental Materials. Submitted to PRD | Physical Review D, 104, L101502 (2021) | 10.1103/PhysRevD.104.L101502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The GRAVITY Collaboration achieved the remarkable detection of the orbital
precession of the S2 star around the Galactic centre supermassive black hole,
providing yet another proof of the validity of the General Relativity. The
departure from the Schwarzschild precession is encoded in the parameter $f_{\rm
SP}$ which multiplies the predicted general relativistic precession. Such a
parameter results to be $f_{\rm SP}=1.10\pm0.19$, which is consistent with
General Relativity ($f_{\rm SP}=1$) at 1$\sigma$ level. Nevertheless, this
parameter may also hide an effect of modified theories of gravity. Thus, we
consider the orbital precession due to the Yukawa-like gravitational potential
arising in the weak field limit of $f(R)$-gravity, and we use the current bound
on the $f_{\rm SP}$ to constrain the strength and the scale length of the
Yukawa-like potential. No deviation from GR are revealed at scale of
$\lambda<6300$ AU with the strength of the Yukawa potential restricted to
$\delta = -0.01_{-0.14}^{+0.61}$.
| [
{
"created": "Sat, 12 Jun 2021 16:53:58 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 2021 12:46:40 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Oct 2021 14:24:38 GMT",
"version": "v3"
}
] | 2021-11-18 | [
[
"de Martino",
"Ivan",
""
],
[
"della Monica",
"Riccardo",
""
],
[
"de Laurentis",
"Mariafelicia",
""
]
] | The GRAVITY Collaboration achieved the remarkable detection of the orbital precession of the S2 star around the Galactic centre supermassive black hole, providing yet another proof of the validity of the General Relativity. The departure from the Schwarzschild precession is encoded in the parameter $f_{\rm SP}$ which multiplies the predicted general relativistic precession. Such a parameter results to be $f_{\rm SP}=1.10\pm0.19$, which is consistent with General Relativity ($f_{\rm SP}=1$) at 1$\sigma$ level. Nevertheless, this parameter may also hide an effect of modified theories of gravity. Thus, we consider the orbital precession due to the Yukawa-like gravitational potential arising in the weak field limit of $f(R)$-gravity, and we use the current bound on the $f_{\rm SP}$ to constrain the strength and the scale length of the Yukawa-like potential. No deviation from GR are revealed at scale of $\lambda<6300$ AU with the strength of the Yukawa potential restricted to $\delta = -0.01_{-0.14}^{+0.61}$. |
2301.06639 | Sizheng Ma | Sizheng Ma, Ling Sun, Yanbei Chen | Using rational filters to uncover the first ringdown overtone in
GW150914 | null | Phys. Rev. D 107, 084010 (2023) | 10.1103/PhysRevD.107.084010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There have been debates in the literature about the existence of the first
overtone in the ringdown of GW150914. We develop a novel Bayesian framework to
reanalyze the data of this event, by incorporating a new technique, the
"rational filter" that can clean particular modes from the ringdown signal. We
examine the existence of the first overtone in GW150914 from multiple novel
perspectives. First, we confirm that the estimates of the remnant black hole
mass and spin are more consistent with those obtained from the full IMR signal
when including the first overtone at an early stage of the ringdown (right
after the inferred signal peak); such improvement fades away at later times.
Second, we formulate a new way to compare the ringdown models with and without
the first overtone by calculating the Bayes factor at different times during
the ringdown. We obtain a Bayes factor of 600 at the time when the signal
amplitude reaches its peak. The Bayes factor decreases sharply when moving away
from the peak time and eventually oscillates around a small value when the
overtone signal is expected to have decayed. Third, we clean the fundamental
mode from the ringdown of GW150914 and estimate the amplitudes of the modes
using the filtered data with MCMC. The inferred amplitude of the fundamental
mode is ~0 whereas the amplitude of the first overtone remains almost
unchanged, implying that the filtered data is consistent with a
first-overtone-only template. Similarly, if we remove the first overtone from
the GW150914 data, the filtered data are consistent with a
fundamental-mode-only template. Finally, after removing the fundamental mode,
we use MCMC to infer the remnant black hole mass and spin from the first
overtone alone. We find the posteriors are still informative and consistent
with those inferred from the fundamental mode.
| [
{
"created": "Mon, 16 Jan 2023 23:48:26 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2023 16:49:14 GMT",
"version": "v2"
}
] | 2023-04-06 | [
[
"Ma",
"Sizheng",
""
],
[
"Sun",
"Ling",
""
],
[
"Chen",
"Yanbei",
""
]
] | There have been debates in the literature about the existence of the first overtone in the ringdown of GW150914. We develop a novel Bayesian framework to reanalyze the data of this event, by incorporating a new technique, the "rational filter" that can clean particular modes from the ringdown signal. We examine the existence of the first overtone in GW150914 from multiple novel perspectives. First, we confirm that the estimates of the remnant black hole mass and spin are more consistent with those obtained from the full IMR signal when including the first overtone at an early stage of the ringdown (right after the inferred signal peak); such improvement fades away at later times. Second, we formulate a new way to compare the ringdown models with and without the first overtone by calculating the Bayes factor at different times during the ringdown. We obtain a Bayes factor of 600 at the time when the signal amplitude reaches its peak. The Bayes factor decreases sharply when moving away from the peak time and eventually oscillates around a small value when the overtone signal is expected to have decayed. Third, we clean the fundamental mode from the ringdown of GW150914 and estimate the amplitudes of the modes using the filtered data with MCMC. The inferred amplitude of the fundamental mode is ~0 whereas the amplitude of the first overtone remains almost unchanged, implying that the filtered data is consistent with a first-overtone-only template. Similarly, if we remove the first overtone from the GW150914 data, the filtered data are consistent with a fundamental-mode-only template. Finally, after removing the fundamental mode, we use MCMC to infer the remnant black hole mass and spin from the first overtone alone. We find the posteriors are still informative and consistent with those inferred from the fundamental mode. |
1402.6723 | Saulo Pereira H | S. H. Pereira, A. Pinho S. S. and J. M. Hoff da Silva | Some remarks on the attractor behaviour in ELKO cosmology | 17 pages, section III with minor changes and section IV rewritten
with a new analysis | JCAP08(2014)020 | 10.1088/1475-7516/2014/08/020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent results on the dynamical stability of a system involving the
interaction of the ELKO spinor field with standard matter in the universe have
been reanalysed, and the conclusion is that such system does not exhibit
isolated stable points that could alleviate the cosmic coincidence problem.
When a constant parameter $\delta$ related to the potential of the ELKO field
is introduced in the system however, stable fixed points are found for some
specific types of interaction between the ELKO field and matter. Although the
parameter $\delta$ is related to an unknown potential, in order to satisfy the
stability conditions and also that the fixed points are real, the range of the
constant parameter $\delta$ can be constrained for the present time and the
coincidence problem can be alleviated for some specific interactions. Such
restriction on the ELKO potential opens possibility to apply the ELKO field as
a candidate to dark energy in the universe, and so explain the present phase of
acceleration of the universe through the decay of the ELKO field into matter.
| [
{
"created": "Wed, 26 Feb 2014 22:00:20 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Aug 2014 14:25:27 GMT",
"version": "v2"
}
] | 2015-02-04 | [
[
"Pereira",
"S. H.",
""
],
[
"S.",
"A. Pinho S.",
""
],
[
"da Silva",
"J. M. Hoff",
""
]
] | Recent results on the dynamical stability of a system involving the interaction of the ELKO spinor field with standard matter in the universe have been reanalysed, and the conclusion is that such system does not exhibit isolated stable points that could alleviate the cosmic coincidence problem. When a constant parameter $\delta$ related to the potential of the ELKO field is introduced in the system however, stable fixed points are found for some specific types of interaction between the ELKO field and matter. Although the parameter $\delta$ is related to an unknown potential, in order to satisfy the stability conditions and also that the fixed points are real, the range of the constant parameter $\delta$ can be constrained for the present time and the coincidence problem can be alleviated for some specific interactions. Such restriction on the ELKO potential opens possibility to apply the ELKO field as a candidate to dark energy in the universe, and so explain the present phase of acceleration of the universe through the decay of the ELKO field into matter. |
0803.1538 | Pierre Martinetti | Pierre Martinetti | Conformal mapping of Unruh temperature | Paper shortened and reorganized. To be published in Modern Physics
Letters A | Mod.Phys.Lett.A24:1473-1483,2009 | 10.1142/S0217732309030874 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thanks to a local interpetation of the KMS condition, the mapping from
(unbounded) wedge regions of Minkowski space-time to (bounded) double-cone
regions is extended to the Unruh temperature associated to relevant observers
in both regions. A previous result, the diamond's temperature, is shown to be
proportional to the inverse of the conformal factor (Weyl rescaling of the
metric) of this map. One thus explains from a mathematical point of view why an
observer with finite lifetime experiences the vacuum as a thermal state
whatever his acceleration, even vanishing.
| [
{
"created": "Tue, 11 Mar 2008 09:08:11 GMT",
"version": "v1"
},
{
"created": "Sat, 2 May 2009 14:50:57 GMT",
"version": "v2"
}
] | 2009-07-22 | [
[
"Martinetti",
"Pierre",
""
]
] | Thanks to a local interpetation of the KMS condition, the mapping from (unbounded) wedge regions of Minkowski space-time to (bounded) double-cone regions is extended to the Unruh temperature associated to relevant observers in both regions. A previous result, the diamond's temperature, is shown to be proportional to the inverse of the conformal factor (Weyl rescaling of the metric) of this map. One thus explains from a mathematical point of view why an observer with finite lifetime experiences the vacuum as a thermal state whatever his acceleration, even vanishing. |
1704.03061 | David McNutt | D. D. McNutt, A. A. Coley, and A. Forget | The Cartan Algorithm in Five Dimensions | 18 pages | Journal of Mathematical Physics, 58 035202, 2017 | 10.1063/1.4977985 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we introduce an algorithm to determine the equivalence of five
dimensional spacetimes, which generalizes the Karlhede algorithm for four
dimensional general relativity. As an alternative to the Petrov type
classification, we employ the alignment classification to algebraically
classify the Weyl tensor. To illustrate the algorithm we discuss three
examples: the singly rotating Myers-Perry solution, the Kerr (anti) de Sitter
solution, and the rotating black ring solution. We briefly discuss some
applications of the Cartan algorithm in five dimensions.
| [
{
"created": "Mon, 10 Apr 2017 21:34:04 GMT",
"version": "v1"
}
] | 2017-04-12 | [
[
"McNutt",
"D. D.",
""
],
[
"Coley",
"A. A.",
""
],
[
"Forget",
"A.",
""
]
] | In this paper we introduce an algorithm to determine the equivalence of five dimensional spacetimes, which generalizes the Karlhede algorithm for four dimensional general relativity. As an alternative to the Petrov type classification, we employ the alignment classification to algebraically classify the Weyl tensor. To illustrate the algorithm we discuss three examples: the singly rotating Myers-Perry solution, the Kerr (anti) de Sitter solution, and the rotating black ring solution. We briefly discuss some applications of the Cartan algorithm in five dimensions. |
1808.04315 | Sandeep Aashish | Sandeep Aashish, Abhilash Padhy, Sukanta Panda and Arun Rana | Inflation with an antisymmetric tensor field | 10 pages; minor correction to the claim of Sec. IV; to appear in EPJ
C | Eur. Phys. J. C (2018) 78: 887 | 10.1140/epjc/s10052-018-6366-z | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility of inflation with models of antisymmetric
tensor field having minimal and nonminimal couplings to gravity. Although the
minimal model does not support inflation, the nonminimal models, through the
introduction of a nonminimal coupling to gravity, can give rise to stable
de-Sitter solutions with a bound on the coupling parameters. The values of
field and coupling parameters are sub-planckian. Slow roll analysis is
performed and slow-roll parameters are defined which can give the required
number of e-folds for sufficient inflation. Stability analysis has been
performed for perturbations to antisymmetric field while keeping the metric
unperturbed, and it is found that only the sub-horizon modes are free of ghost
instability for de-Sitter space.
| [
{
"created": "Mon, 13 Aug 2018 16:16:14 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Sep 2018 06:23:29 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Oct 2018 02:41:14 GMT",
"version": "v3"
}
] | 2018-11-02 | [
[
"Aashish",
"Sandeep",
""
],
[
"Padhy",
"Abhilash",
""
],
[
"Panda",
"Sukanta",
""
],
[
"Rana",
"Arun",
""
]
] | We investigate the possibility of inflation with models of antisymmetric tensor field having minimal and nonminimal couplings to gravity. Although the minimal model does not support inflation, the nonminimal models, through the introduction of a nonminimal coupling to gravity, can give rise to stable de-Sitter solutions with a bound on the coupling parameters. The values of field and coupling parameters are sub-planckian. Slow roll analysis is performed and slow-roll parameters are defined which can give the required number of e-folds for sufficient inflation. Stability analysis has been performed for perturbations to antisymmetric field while keeping the metric unperturbed, and it is found that only the sub-horizon modes are free of ghost instability for de-Sitter space. |
1605.03431 | Tony Scott C. | T. C. Scott, Xiangdong Zhang, R. B. Mann and G. J. Fee | Canonical reduction for dilatonic gravity in 3+1 dimensions | Sequel to arXiv:gr-qc/0611144, doi:10.1088/0264-9381/24/18/006 | Physical Review D 93, 084017 (2016) | 10.1103/PhysRevD.93.084017. | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the 1+1-dimensional gravity formalism of Ohta and Mann to 3+1
dimensions by developing the canonical reduction of a proposed formalism
applied to a system coupled with a set of point particles. This is done via the
Arnowitt-Deser-Misner method and by eliminating the resulting constraints and
imposing coordinate conditions. The reduced Hamiltonian is completely
determined in terms of the particles' canonical variables (coordinates, dilaton
field and momenta). It is found that the equation governing the dilaton field
under suitable gauge and coordinate conditions, including the absence of
transverse-traceless metric components, is a logarithmic Schroedinger equation.
Thus, although different, the 3+1 formalism retains some essential features of
the earlier 1+1 formalism, in particular the means of obtaining a quantum
theory for dilatonic gravity.
| [
{
"created": "Wed, 11 May 2016 13:23:39 GMT",
"version": "v1"
}
] | 2016-05-12 | [
[
"Scott",
"T. C.",
""
],
[
"Zhang",
"Xiangdong",
""
],
[
"Mann",
"R. B.",
""
],
[
"Fee",
"G. J.",
""
]
] | We generalize the 1+1-dimensional gravity formalism of Ohta and Mann to 3+1 dimensions by developing the canonical reduction of a proposed formalism applied to a system coupled with a set of point particles. This is done via the Arnowitt-Deser-Misner method and by eliminating the resulting constraints and imposing coordinate conditions. The reduced Hamiltonian is completely determined in terms of the particles' canonical variables (coordinates, dilaton field and momenta). It is found that the equation governing the dilaton field under suitable gauge and coordinate conditions, including the absence of transverse-traceless metric components, is a logarithmic Schroedinger equation. Thus, although different, the 3+1 formalism retains some essential features of the earlier 1+1 formalism, in particular the means of obtaining a quantum theory for dilatonic gravity. |
2303.03130 | Alexander Zhidenko | R. A. Konoplya and A. Zhidenko | General black-hole metric mimicking Schwarzschild spacetime | 9 pages (REVTeX), 3 figures | JCAP 08 (2023) 008 | 10.1088/1475-7516/2023/08/008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the general parametrization of spherically symmetric and asymptotically
flat black holes in arbitrary metric theories of gravity and implying that: a)
the post-Newtonian constraints are taken into account and b) basic
astrophysically relevant characteristics (such as, dominant quasinormal modes,
frequency at the innermost stable circular orbit, binding energy, radius of the
shadow etc.) are indistinguishable from their Schwarzschild values, we propose
a simple metric which depends on three independent parameters (coefficients of
the parametrization). Variation of these three parameters can, nevertheless,
lead to the two distinctive features. The first is the black-hole temperature,
and consequently the Hawking radiation, which can differ a lot from its
Schwarzschild limit. The second is the outburst of overtones which become
extremely sensitive to small changes of the parameters.
| [
{
"created": "Mon, 6 Mar 2023 13:47:20 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Mar 2023 20:29:34 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Aug 2023 18:28:17 GMT",
"version": "v3"
}
] | 2023-08-10 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Using the general parametrization of spherically symmetric and asymptotically flat black holes in arbitrary metric theories of gravity and implying that: a) the post-Newtonian constraints are taken into account and b) basic astrophysically relevant characteristics (such as, dominant quasinormal modes, frequency at the innermost stable circular orbit, binding energy, radius of the shadow etc.) are indistinguishable from their Schwarzschild values, we propose a simple metric which depends on three independent parameters (coefficients of the parametrization). Variation of these three parameters can, nevertheless, lead to the two distinctive features. The first is the black-hole temperature, and consequently the Hawking radiation, which can differ a lot from its Schwarzschild limit. The second is the outburst of overtones which become extremely sensitive to small changes of the parameters. |
0802.1978 | Claus Kiefer | Mark Albers, Claus Kiefer, Marcel Reginatto | Measurement Analysis and Quantum Gravity | 31 pages, many conceptual clarifications included, new appendix
added, to appear in Phys. Rev. D | Phys.Rev.D78:064051,2008 | 10.1103/PhysRevD.78.064051 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the question of whether consistency arguments based on
measurement theory show that the gravitational field must be quantized.
Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type
measurement analysis to a coupled system that consists of a gravitational wave
interacting with a mass cube. We also review the arguments of Eppley and Hannah
and of DeWitt, and investigate a second model in which a gravitational wave
interacts with a quantized scalar field. We argue that one cannot conclude from
the existing gedanken experiments that gravity has to be quantized. Despite the
many physical arguments which speak in favor of a quantum theory of gravity, it
appears that the justification for such a theory must be based on empirical
tests and does not follow from logical arguments alone.
| [
{
"created": "Thu, 14 Feb 2008 08:57:57 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Aug 2008 13:26:15 GMT",
"version": "v2"
}
] | 2009-02-23 | [
[
"Albers",
"Mark",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Reginatto",
"Marcel",
""
]
] | We consider the question of whether consistency arguments based on measurement theory show that the gravitational field must be quantized. Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type measurement analysis to a coupled system that consists of a gravitational wave interacting with a mass cube. We also review the arguments of Eppley and Hannah and of DeWitt, and investigate a second model in which a gravitational wave interacts with a quantized scalar field. We argue that one cannot conclude from the existing gedanken experiments that gravity has to be quantized. Despite the many physical arguments which speak in favor of a quantum theory of gravity, it appears that the justification for such a theory must be based on empirical tests and does not follow from logical arguments alone. |
1102.4538 | Valent Galliano | Galliano Valent | Further results on non-diagonal Bianchi type III vacuum metrics | 21 pages, no figures | null | 10.1007/s10714-012-1340-9 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the derivation, for these vacuum metrics, of the Painlev\'e VI
equation first obtained by Christodoulakis and Terzis, from the field equations
for both minkowskian and euclidean signatures. This allows a complete
discussion and the precise connection with some old results due to Kinnersley.
The hyperk\"ahler metrics are shown to belong to the Multi-Centre class and for
the cases exhibiting an integrable geodesic flow the relevant Killing tensors
are given. We conclude by the proof that for the Bianchi B family, excluding
type III, there are no hyperk\"ahler metrics.
| [
{
"created": "Tue, 22 Feb 2011 15:39:38 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Valent",
"Galliano",
""
]
] | We present the derivation, for these vacuum metrics, of the Painlev\'e VI equation first obtained by Christodoulakis and Terzis, from the field equations for both minkowskian and euclidean signatures. This allows a complete discussion and the precise connection with some old results due to Kinnersley. The hyperk\"ahler metrics are shown to belong to the Multi-Centre class and for the cases exhibiting an integrable geodesic flow the relevant Killing tensors are given. We conclude by the proof that for the Bianchi B family, excluding type III, there are no hyperk\"ahler metrics. |
1810.04399 | Dieter Heiss | WD Heiss | An effective interaction at the Planck mass and Planck length | 4 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A simple model is suggested by assuming an effective interaction at the
crossing point of the two curves, the Schwarzschild radius and the Compton wave
length, that is at the Planck length and Planck mass. It is argued that there
would be a physical effect that may be measurable at, say, nucleon mass and
size, while the Schwarzschild radius would remain unaffected for macroscopic
lengths and masses.
| [
{
"created": "Wed, 10 Oct 2018 07:46:12 GMT",
"version": "v1"
}
] | 2018-10-11 | [
[
"Heiss",
"WD",
""
]
] | A simple model is suggested by assuming an effective interaction at the crossing point of the two curves, the Schwarzschild radius and the Compton wave length, that is at the Planck length and Planck mass. It is argued that there would be a physical effect that may be measurable at, say, nucleon mass and size, while the Schwarzschild radius would remain unaffected for macroscopic lengths and masses. |
2103.12272 | Ying Wang | Ying Wang, Wei Sun, Fuyao Liu, Xin Wu | Construction of explicit symplectic integrators in general relativity.
III. Reissner-Nordstrom-(anti)-de Sitter black holes | 15pages,26figures | null | 10.3847/1538-4365/abf116 | null | gr-qc astro-ph.IM nlin.CD physics.comp-ph | http://creativecommons.org/licenses/by/4.0/ | We give a possible splitting method to a Hamiltonian for the description of
charged particles moving around the Reissner-Nordstrom-(anti)-de Sitter black
hole with an external magnetic field. This Hamiltonian can be separated into
six analytical solvable pieces, whose solutions are explicit functions of
proper time. In this case, second- and fourth-order explicit symplectic
integrators are easily available. They exhibit excellent long-term behavior in
maintaining the boundness of Hamiltonian errors regardless of ordered or
chaotic orbits if appropriate step-sizes are chosen. Under some circumstances,
an increase of positive cosmological constant gives rise to strengthening the
extent of chaos from the global phase space; namely, chaos of charged particles
occurs easily for the accelerated expansion of the universe. However, an
increase of the magnitude of negative cosmological constant does not. The
different contributions on chaos are because the cosmological constant acts as
a repulsive force in the Reissner-Nordstrom-de Sitter black hole, but an
attractive force in the Reissner-Nordstrom-anti-de Sitter black hole.
| [
{
"created": "Tue, 23 Mar 2021 02:44:50 GMT",
"version": "v1"
}
] | 2021-05-05 | [
[
"Wang",
"Ying",
""
],
[
"Sun",
"Wei",
""
],
[
"Liu",
"Fuyao",
""
],
[
"Wu",
"Xin",
""
]
] | We give a possible splitting method to a Hamiltonian for the description of charged particles moving around the Reissner-Nordstrom-(anti)-de Sitter black hole with an external magnetic field. This Hamiltonian can be separated into six analytical solvable pieces, whose solutions are explicit functions of proper time. In this case, second- and fourth-order explicit symplectic integrators are easily available. They exhibit excellent long-term behavior in maintaining the boundness of Hamiltonian errors regardless of ordered or chaotic orbits if appropriate step-sizes are chosen. Under some circumstances, an increase of positive cosmological constant gives rise to strengthening the extent of chaos from the global phase space; namely, chaos of charged particles occurs easily for the accelerated expansion of the universe. However, an increase of the magnitude of negative cosmological constant does not. The different contributions on chaos are because the cosmological constant acts as a repulsive force in the Reissner-Nordstrom-de Sitter black hole, but an attractive force in the Reissner-Nordstrom-anti-de Sitter black hole. |
1707.02943 | Robert Sims | Stephon Alexander, Sam Cormack, David Lowe, Robert Sims | On the Classical and Quantum Stability of a Cosmic Ghost | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ghost fields have reemerged in a handful of phenomenologically motivated
cosmological and particle physics scenarios, and most recently in a cyclic
mechanism to address the fine-tuning of gauge couplings in the standard model.
We study the classical and quantum stability of a ghost-dilaton system coupled
to a gauge sector and find that this system is classically stable due to the
existence of limit cycles in phase space. We also analyze the coupled gauge
invariant classical perturbations and find a range of phenomenologically viable
parameters where the system is stable. We also discuss ways to avoid both
quantum and vacuum instabilities by either having a ghost condensate or
Classicon configurations.
| [
{
"created": "Mon, 10 Jul 2017 16:47:58 GMT",
"version": "v1"
}
] | 2017-07-11 | [
[
"Alexander",
"Stephon",
""
],
[
"Cormack",
"Sam",
""
],
[
"Lowe",
"David",
""
],
[
"Sims",
"Robert",
""
]
] | Ghost fields have reemerged in a handful of phenomenologically motivated cosmological and particle physics scenarios, and most recently in a cyclic mechanism to address the fine-tuning of gauge couplings in the standard model. We study the classical and quantum stability of a ghost-dilaton system coupled to a gauge sector and find that this system is classically stable due to the existence of limit cycles in phase space. We also analyze the coupled gauge invariant classical perturbations and find a range of phenomenologically viable parameters where the system is stable. We also discuss ways to avoid both quantum and vacuum instabilities by either having a ghost condensate or Classicon configurations. |
1110.2379 | Orfeu Bertolami | Orfeu Bertolami, Ant\'onio Martins | On the dynamics of perfect fluids in non-minimally coupled gravity | 7 pages, 3 figures | null | 10.1103/PhysRevD.85.024012 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore the consequences that a non-minimal coupling between
geometry and matter can have on the dynamics of perfect fluids. It is argued
that the presence of a static, axially symmetric pressureless fluid does not
imply a Minkowski space-time like as is in General Relativity. This feature can
be atributed to a pressure mimicking mechanism related to the non-minimal
coupling. The case of a spherically symmetric black hole surrounded by fluid
matter is analyzed, and it is shown that under equilibrium conditions the total
fluid mass is about twice that of the black hole. Finally, a generalization of
the Newtonian potential for a fluid element is proposed and its implications
are briefly discussed.
| [
{
"created": "Tue, 11 Oct 2011 13:52:48 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Martins",
"António",
""
]
] | In this work we explore the consequences that a non-minimal coupling between geometry and matter can have on the dynamics of perfect fluids. It is argued that the presence of a static, axially symmetric pressureless fluid does not imply a Minkowski space-time like as is in General Relativity. This feature can be atributed to a pressure mimicking mechanism related to the non-minimal coupling. The case of a spherically symmetric black hole surrounded by fluid matter is analyzed, and it is shown that under equilibrium conditions the total fluid mass is about twice that of the black hole. Finally, a generalization of the Newtonian potential for a fluid element is proposed and its implications are briefly discussed. |
gr-qc/0103114 | David Blashke | D. Blaschke, V. Pervushin, D. Proskurin, S. Vinitsky, A. Gusev | Cosmological Creation of Vector Bosons and Fermions | 20 pages, 1 figure, discussion extended, typos corrected | null | null | JINR-E2-2001-52 | gr-qc astro-ph | null | The cosmological creation of primordial vector bosons and fermions is
described in the Standard Model of strong and electro-weak interactions given
in a space-time with the relative standard of measurement of geometric
intervals. Using the reparametrization - invariant perturbation theory and the
holomorphic representation of quantized fields we derive equations for the
Bogoliubov coefficients and distribution functions of created particles. The
main result is the intensive cosmological creation of longitudinal Z and W
bosons (due to their mass singularity) by the universe in the rigid state. We
introduce the hypothesis that the decay of the primordially created vector
bosons is the origin of the Cosmic Microwave Background radiation.
| [
{
"created": "Fri, 30 Mar 2001 21:34:14 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jun 2001 03:35:54 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Blaschke",
"D.",
""
],
[
"Pervushin",
"V.",
""
],
[
"Proskurin",
"D.",
""
],
[
"Vinitsky",
"S.",
""
],
[
"Gusev",
"A.",
""
]
] | The cosmological creation of primordial vector bosons and fermions is described in the Standard Model of strong and electro-weak interactions given in a space-time with the relative standard of measurement of geometric intervals. Using the reparametrization - invariant perturbation theory and the holomorphic representation of quantized fields we derive equations for the Bogoliubov coefficients and distribution functions of created particles. The main result is the intensive cosmological creation of longitudinal Z and W bosons (due to their mass singularity) by the universe in the rigid state. We introduce the hypothesis that the decay of the primordially created vector bosons is the origin of the Cosmic Microwave Background radiation. |
1908.06654 | Oscar Castillo Felisola Dr. | Oscar Castillo-Felisola and Jose Perdiguero and Oscar Orellana and
Alfonso R. Zerwekh | Emergent metric and geodesic analysis in cosmological solutions of
(torsion-free) Polynomial Affine Gravity | 19 pages, 4 figures. Comments are welcome | null | 10.1088/1361-6382/ab58ef | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Starting from an affinely connected space, we consider a model of gravity
whose fundamental field is the connection. We build up the action using as sole
premise the invariance under diffeomorphisms, and study the consequences of a
cosmological ansatz for the affine connection in the torsion-free sector.
Although the model is built without requiring a metric, we show that the
nondegenerated Ricci curvature of the affine connection can be interpreted as
an \emph{emergent} metric on the manifold. We show that there exists a
parametrization in which the \((r,\varphi)\)-restriction of the geodesics
coincides with that of the Friedman--Robertson--Walker model. Additionally, for
connections with nondegenerated Ricci we are able to distinguish between
space-, time- and null-like self-parallel curves, providing a way to
differentiate \emph{trajectories} of massive and massless particles.
| [
{
"created": "Mon, 19 Aug 2019 09:10:46 GMT",
"version": "v1"
}
] | 2020-04-08 | [
[
"Castillo-Felisola",
"Oscar",
""
],
[
"Perdiguero",
"Jose",
""
],
[
"Orellana",
"Oscar",
""
],
[
"Zerwekh",
"Alfonso R.",
""
]
] | Starting from an affinely connected space, we consider a model of gravity whose fundamental field is the connection. We build up the action using as sole premise the invariance under diffeomorphisms, and study the consequences of a cosmological ansatz for the affine connection in the torsion-free sector. Although the model is built without requiring a metric, we show that the nondegenerated Ricci curvature of the affine connection can be interpreted as an \emph{emergent} metric on the manifold. We show that there exists a parametrization in which the \((r,\varphi)\)-restriction of the geodesics coincides with that of the Friedman--Robertson--Walker model. Additionally, for connections with nondegenerated Ricci we are able to distinguish between space-, time- and null-like self-parallel curves, providing a way to differentiate \emph{trajectories} of massive and massless particles. |
2301.00724 | Frans Klinkhamer | F.R. Klinkhamer | Defect wormhole: A traversable wormhole without exotic matter | 20 pages, 5 figures, v8: published version | Acta Phys. Polon. B 54, 5-A3 (2023) | 10.5506/APhysPolB.54.5-A3 | KA-TP-31-2022 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a traversable-wormhole solution of the gravitational field
equation of General Relativity without need of exotic matter (exotic matter
can, for example, have negative energy density and vanishing isotropic
pressure). Instead of exotic matter, the solution relies on a 3-dimensional
"spacetime defect" characterized by a locally vanishing metric determinant.
| [
{
"created": "Fri, 30 Dec 2022 18:29:15 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jan 2023 16:29:50 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Jan 2023 15:35:20 GMT",
"version": "v3"
},
{
"created": "Mon, 6 Feb 2023 15:44:28 GMT",
"version": "v4"
},
{
"cre... | 2023-06-16 | [
[
"Klinkhamer",
"F. R.",
""
]
] | We present a traversable-wormhole solution of the gravitational field equation of General Relativity without need of exotic matter (exotic matter can, for example, have negative energy density and vanishing isotropic pressure). Instead of exotic matter, the solution relies on a 3-dimensional "spacetime defect" characterized by a locally vanishing metric determinant. |
gr-qc/9909020 | Eric Gourgoulhon | S. Bonazzola, E. Gourgoulhon, P. Grandclement and J.-A. Marck (DARC,
CNRS, Observatoire de Paris) | Darwin-Riemann problems in general relativity | 20 pages, 11 PostScript figures, uses PTPTeX, to appear in the
Proceedings of Yukawa International Seminar 99 "Black Holes and Gravitational
Waves", edited by T. Nakamura & H. Kodama, Prog. Theor. Phys. Suppl | Prog.Theor.Phys.Suppl.136:216,1999 | 10.1143/PTPS.136.216 | null | gr-qc | null | A review is given of recent results about the computation of irrotational
Darwin-Riemann configurations in general relativity. Such configurations are
expected to represent fairly well the late stages of inspiralling binary
neutron stars.
| [
{
"created": "Mon, 6 Sep 1999 12:40:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bonazzola",
"S.",
"",
"DARC,\n CNRS, Observatoire de Paris"
],
[
"Gourgoulhon",
"E.",
"",
"DARC,\n CNRS, Observatoire de Paris"
],
[
"Grandclement",
"P.",
"",
"DARC,\n CNRS, Observatoire de Paris"
],
[
"Marck",
"J. -A.",
"",
"DARC,\n ... | A review is given of recent results about the computation of irrotational Darwin-Riemann configurations in general relativity. Such configurations are expected to represent fairly well the late stages of inspiralling binary neutron stars. |
1911.11203 | Steven Carlip | S. Carlip | A comment on "How the cosmological constant is hidden by Planck scale
curvature fluctuations'' | 5 pages, reply to arXiv:1911.06110 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent preprint by Wang and Unruh [arXiv:1911.06110] contains a number of
criticisms of my paper, "Hiding the cosmological constant" [Phys. Rev. Lett.
123 (2019) 131302, arXiv:1809.08277]. While Wang and Unruh suggest an
interesting alternative scenario and raise an important conceptual question,
most of their criticisms are incorrect, in part because of misunderstandings
about averaging and about the nature of the "foamy" spacetimes considered in my
paper.
| [
{
"created": "Mon, 25 Nov 2019 20:10:47 GMT",
"version": "v1"
}
] | 2019-11-27 | [
[
"Carlip",
"S.",
""
]
] | A recent preprint by Wang and Unruh [arXiv:1911.06110] contains a number of criticisms of my paper, "Hiding the cosmological constant" [Phys. Rev. Lett. 123 (2019) 131302, arXiv:1809.08277]. While Wang and Unruh suggest an interesting alternative scenario and raise an important conceptual question, most of their criticisms are incorrect, in part because of misunderstandings about averaging and about the nature of the "foamy" spacetimes considered in my paper. |
gr-qc/0310004 | Stefano Ansoldi | Stefano Ansoldi | WKB metastable quantum states of a de Sitter--Reissner-Nordstroem dust
shell | IOPart class, 16 figures | Class.Quant.Grav. 19 (2002) 6321-6344 | 10.1088/0264-9381/19/24/304 | null | gr-qc | null | We study the dynamics of a spherically symmetric dust shell separating two
spacetime domains, the 'interior' one being a part of the de Sitter spacetime
and the exterior one having the 'extremal' Reissner-Nordstroem geometry.
Extending the ideas of previous works on the subject, we show that the it is
possible to determine the (metastable) WKB quantum states of this gravitational
system.
| [
{
"created": "Wed, 1 Oct 2003 13:46:04 GMT",
"version": "v1"
}
] | 2022-05-04 | [
[
"Ansoldi",
"Stefano",
""
]
] | We study the dynamics of a spherically symmetric dust shell separating two spacetime domains, the 'interior' one being a part of the de Sitter spacetime and the exterior one having the 'extremal' Reissner-Nordstroem geometry. Extending the ideas of previous works on the subject, we show that the it is possible to determine the (metastable) WKB quantum states of this gravitational system. |
0811.3068 | Zong-Kuan Guo | Zong-Kuan Guo, Nobuyoshi Ohta, Takashi Torii | Black Holes in the Dilatonic Einstein-Gauss-Bonnet Theory in Various
Dimensions II -- Asymptotically AdS Topological Black Holes -- | 24 pages, 8 figures, PTPTeX, typos corrected | Prog.Theor.Phys.121:253-273,2009 | 10.1143/PTP.121.253 | KU-TP 024 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study asymptotically AdS topological black hole solutions with k=0 (plane
symmetric) in the Einstein gravity with Gauss-Bonnet term, the dilaton and a
"cosmological constant" in various dimensions. We derive the field equations
for suitable ansatz for general D dimensions. We determine the parameter
regions including dilaton couplings where such solutions exist and construct
black hole solutions of various masses numerically in D=4,5,6 and 10
dimensional spacetime with (D-2)-dimensional hypersurface of zero curvature.
| [
{
"created": "Wed, 19 Nov 2008 09:19:50 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jan 2009 13:43:28 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Feb 2009 12:19:48 GMT",
"version": "v3"
}
] | 2009-12-04 | [
[
"Guo",
"Zong-Kuan",
""
],
[
"Ohta",
"Nobuyoshi",
""
],
[
"Torii",
"Takashi",
""
]
] | We study asymptotically AdS topological black hole solutions with k=0 (plane symmetric) in the Einstein gravity with Gauss-Bonnet term, the dilaton and a "cosmological constant" in various dimensions. We derive the field equations for suitable ansatz for general D dimensions. We determine the parameter regions including dilaton couplings where such solutions exist and construct black hole solutions of various masses numerically in D=4,5,6 and 10 dimensional spacetime with (D-2)-dimensional hypersurface of zero curvature. |
gr-qc/0411066 | Yongge Ma | Li-e Qiang, Yongge Ma, Muxin Han, Dan Yu | 5-dimensional Brans-Dicke Theory and Cosmic Acceleration | 13 pages, 4 figures, revised version to appear in PRD | Phys.Rev. D71 (2005) 061501 | 10.1103/PhysRevD.71.061501 | null | gr-qc astro-ph hep-th | null | We consider a 5-dimensional scalar-tensor theory which is a direct
generalization of the original 4-dimensional Brans-Dicke theory to
5-dimensions. By assuming that there is a hypersurface-orthogonal spacelike
Killing vector field in the underlying 5-dimensional spacetime, the theory is
reduced to a 4-dimensional theory where the 4-metric is coupled with two scalar
fields. The cosmological implication of this reduced theory is then studied in
the Robertson-Walker model. It turns out that the two scalar fields may account
naturally for the present accelerated expansion of our universe. The
observational restriction of the reduced cosmological model is also analyzed.
| [
{
"created": "Sun, 14 Nov 2004 14:59:02 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2005 07:00:37 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Qiang",
"Li-e",
""
],
[
"Ma",
"Yongge",
""
],
[
"Han",
"Muxin",
""
],
[
"Yu",
"Dan",
""
]
] | We consider a 5-dimensional scalar-tensor theory which is a direct generalization of the original 4-dimensional Brans-Dicke theory to 5-dimensions. By assuming that there is a hypersurface-orthogonal spacelike Killing vector field in the underlying 5-dimensional spacetime, the theory is reduced to a 4-dimensional theory where the 4-metric is coupled with two scalar fields. The cosmological implication of this reduced theory is then studied in the Robertson-Walker model. It turns out that the two scalar fields may account naturally for the present accelerated expansion of our universe. The observational restriction of the reduced cosmological model is also analyzed. |
2007.10068 | Tan Liu | Tan Liu, Wen Zhao, Yan Wang | Gravitational waveforms from the quasicircular inspiral of compact
binaries in massive Brans-Dicke theory | 23 pages, accepted for publication in PRD | Phys. Rev. D 102, 124035 (2020) | 10.1103/PhysRevD.102.124035 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We study the gravitational waves emitted by an inspiralling compact binary
system in massive Brans-Dicke theory. In addition to the two tensor
polarizations, which have been obtained in the previous work, we calculate
explicitly and analytically the expressions for the time-domain waveforms of
the two scalar polarizations. With the stationary phase approximations, we
obtain the Fourier transforms of the two tensor polarizations. We find that
when the scalar field is light, the waveforms can be mapped to the parametrized
post-Einsteinian (ppE) framework and we identify the ppE parameters. However,
when the scalar field is heavy, the ppE framework is not applicable. We also
obtain the projected constraints on the parameters of this theory by
gravitational wave observations of future ground-based detectors. Finally, we
apply our result to the model proposed by Damour and Esposito-Far\`{e}se,
$f(R)$ gravity, and screened modified gravity.
| [
{
"created": "Mon, 20 Jul 2020 12:58:30 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Nov 2020 05:24:00 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Liu",
"Tan",
""
],
[
"Zhao",
"Wen",
""
],
[
"Wang",
"Yan",
""
]
] | We study the gravitational waves emitted by an inspiralling compact binary system in massive Brans-Dicke theory. In addition to the two tensor polarizations, which have been obtained in the previous work, we calculate explicitly and analytically the expressions for the time-domain waveforms of the two scalar polarizations. With the stationary phase approximations, we obtain the Fourier transforms of the two tensor polarizations. We find that when the scalar field is light, the waveforms can be mapped to the parametrized post-Einsteinian (ppE) framework and we identify the ppE parameters. However, when the scalar field is heavy, the ppE framework is not applicable. We also obtain the projected constraints on the parameters of this theory by gravitational wave observations of future ground-based detectors. Finally, we apply our result to the model proposed by Damour and Esposito-Far\`{e}se, $f(R)$ gravity, and screened modified gravity. |
1703.06781 | Dr. Sudhaker Upadhyay | Sudhaker Upadhyay | Thermodynamics and galactic clustering with a modified gravitational
potential | 13 pages, 4 figures, revtex4 | Phys. Rev. D 95, 043008 (2017) | 10.1103/PhysRevD.95.043008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on thermodynamics, we study the galactic clustering of an expanding
Universe by considering the logarithmic and volume (quantum) corrections to
Newton's law along with the repulsive effect of a harmonic force induced by the
cosmological constant ($\Lambda$) in the formation of the large scale structure
of the Universe. We derive the $N$-body partition function for extended-mass
galaxies (galaxies with halos) analytically. For this partition function, we
compute the exact equations of states, which exhibit the logarithmic, volume
and cosmological constant corrections. In this setting, a modified correlation
(clustering) parameter (due to these corrections) emerges naturally from the
exact equations of state. We compute a corrected grand canonical distribution
function for this system. Furthermore, we obtain a deviation in differential
forms of the two-point correlation functions for both the point-mass and
extended-mass cases. The consequences of these deviations on the correlation
function's power law are also discussed.
| [
{
"created": "Fri, 17 Mar 2017 12:13:54 GMT",
"version": "v1"
}
] | 2017-03-22 | [
[
"Upadhyay",
"Sudhaker",
""
]
] | Based on thermodynamics, we study the galactic clustering of an expanding Universe by considering the logarithmic and volume (quantum) corrections to Newton's law along with the repulsive effect of a harmonic force induced by the cosmological constant ($\Lambda$) in the formation of the large scale structure of the Universe. We derive the $N$-body partition function for extended-mass galaxies (galaxies with halos) analytically. For this partition function, we compute the exact equations of states, which exhibit the logarithmic, volume and cosmological constant corrections. In this setting, a modified correlation (clustering) parameter (due to these corrections) emerges naturally from the exact equations of state. We compute a corrected grand canonical distribution function for this system. Furthermore, we obtain a deviation in differential forms of the two-point correlation functions for both the point-mass and extended-mass cases. The consequences of these deviations on the correlation function's power law are also discussed. |
gr-qc/0110048 | Ulrich H. Gerlach | Ulrich H. Gerlach | Radiation from Violently Accelerated Bodies | 29 pages, 1 figure, Revtex | Phys.Rev. D64 (2001) 105004 | 10.1103/PhysRevD.64.105004 | null | gr-qc | null | A determination is made of the radiation emitted by a linearly uniformly
accelerated uncharged dipole transmitter. It is found that, first of all, the
radiation rate is given by the familiar Larmor formula, but it is augmented by
an amount which becomes dominant for sufficiently high acceleration. For an
accelerated dipole oscillator, the criterion is that the center of mass motion
become relativistic within one oscillation period. The augmented formula and
the measurements which it summarizes presuppose an expanding inertial
observation frame. A static inertial reference frame will not do. Secondly, it
is found that the radiation measured in the expanding inertial frame is
received with 100% fidelity. There is no blueshift or redshift due to the
accelerative motion of the transmitter. Finally, it is found that a pair of
coherently radiating oscillators accelerating (into opposite directions) in
their respective causally disjoint Rindler-coordinatized sectors produces an
interference pattern in the expanding inertial frame. Like the pattern of a
Young double slit interferometer, this Rindler interferometer pattern has a
fringe spacing which is inversely proportional to the proper separation and the
proper frequency of the accelerated sources. The interferometer, as well as the
augmented Larmor formula, provide a unifying perspective. It joins adjacent
Rindler-coordinatized neighborhoods into a single spacetime arena for
scattering and radiation from accelerated bodies.
| [
{
"created": "Tue, 9 Oct 2001 17:38:08 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gerlach",
"Ulrich H.",
""
]
] | A determination is made of the radiation emitted by a linearly uniformly accelerated uncharged dipole transmitter. It is found that, first of all, the radiation rate is given by the familiar Larmor formula, but it is augmented by an amount which becomes dominant for sufficiently high acceleration. For an accelerated dipole oscillator, the criterion is that the center of mass motion become relativistic within one oscillation period. The augmented formula and the measurements which it summarizes presuppose an expanding inertial observation frame. A static inertial reference frame will not do. Secondly, it is found that the radiation measured in the expanding inertial frame is received with 100% fidelity. There is no blueshift or redshift due to the accelerative motion of the transmitter. Finally, it is found that a pair of coherently radiating oscillators accelerating (into opposite directions) in their respective causally disjoint Rindler-coordinatized sectors produces an interference pattern in the expanding inertial frame. Like the pattern of a Young double slit interferometer, this Rindler interferometer pattern has a fringe spacing which is inversely proportional to the proper separation and the proper frequency of the accelerated sources. The interferometer, as well as the augmented Larmor formula, provide a unifying perspective. It joins adjacent Rindler-coordinatized neighborhoods into a single spacetime arena for scattering and radiation from accelerated bodies. |
1011.1088 | Jose Luis Hernandez-Pastora | J.L. Hernandez-Pastora and J. Ospino | From geodesics of the multipole solutions to the perturbed Kepler
problem | null | Phys.Rev.D82:104001,2010 | 10.1103/PhysRevD.82.104001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A static and axisymmetric solution of the Einstein vacuum equations with a
finite number of Relativistic Multipole Moments (RMM) is written in MSA
coordinates up to certain order of approximation, and the structure of its
metric components is explicitly shown. From the equation of equatorial
geodesics we obtain the Binet equation for the orbits and it allows us to
determine the gravitational potential that leads to the equivalent classical
orbital equations of the perturbed Kepler problem. The relativistic corrections
to Keplerian motion are provided by the different contributions of the RMM of
the source starting from the Monopole (Schwarzschild correction). In
particular, the perihelion precession of the orbit is calculated in terms of
the quadrupole and 2$^4$-pole moments. Since the MSA coordinates generalize the
Schwarzschild coordinates, the result obtained allows measurement of the
relevance of the quadrupole moment in the first order correction to the
perihelion frequency-shift.
| [
{
"created": "Thu, 4 Nov 2010 09:21:51 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Hernandez-Pastora",
"J. L.",
""
],
[
"Ospino",
"J.",
""
]
] | A static and axisymmetric solution of the Einstein vacuum equations with a finite number of Relativistic Multipole Moments (RMM) is written in MSA coordinates up to certain order of approximation, and the structure of its metric components is explicitly shown. From the equation of equatorial geodesics we obtain the Binet equation for the orbits and it allows us to determine the gravitational potential that leads to the equivalent classical orbital equations of the perturbed Kepler problem. The relativistic corrections to Keplerian motion are provided by the different contributions of the RMM of the source starting from the Monopole (Schwarzschild correction). In particular, the perihelion precession of the orbit is calculated in terms of the quadrupole and 2$^4$-pole moments. Since the MSA coordinates generalize the Schwarzschild coordinates, the result obtained allows measurement of the relevance of the quadrupole moment in the first order correction to the perihelion frequency-shift. |
2210.02610 | Hee-Suk Cho | Hee-Suk Cho | Measurability of neutron star tidal deformability from merging neutron
star-black hole binaries | 16 pages, 19 figures, accepted for publication in PRD | null | 10.1103/PhysRevD.106.084056 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The neutron star-black hole binary (NSBH) system has been considered one of
the promising detection candidates for ground-based gravitational-wave (GW)
detectors such as LIGO and Virgo. The tidal effects of neutron stars (NSs) are
imprinted on the GW signals emitted from NSBHs as well as binary neutron stars.
In this work, we study how accurately the parameter $\lambda_{\rm NS}$ can be
measured in GW parameter estimation for NSBH signals. We set the parameter
range for the NSBH sources to $[4M_{\odot}, 10M_{\odot}]$ for the black hole
mass, $[1M_{\odot}, 2M_{\odot}]$ for the NS mass, and $[-0.9, 0.9]$ for the
dimensionless black hole spin. For realistic populations of sources distributed
in different parameter spaces, we calculate the measurement errors of
$\lambda_{\rm NS}$ ($\sigma_{\lambda_{\rm NS}}$) using the Fisher matrix
method. In particular, we perform a single-detector analysis using the advanced
LIGO and the Cosmic Explorer detectors and a multi-detector analysis using the
2G (advanced LIGO-Hanford, advanced LIGO-Livingstone, advanced Virgo, and
KAGRA) and the 3G (Einstein Telescope and Cosmic Explorer) networks. We show
the distribution of $\sigma_{\lambda_{\rm NS}}$ for the population of sources
as a one-dimensional probability density function. Our result shows that the
probability density function curves are similar in shape between advanced LIGO
and Cosmic Explorer, but Cosmic Explorer can achieve $\sim 15$ times better
accuracy overall in the measurement of $\lambda_{\rm NS}$. In the case of the
network detectors, the probability density functions are maximum at
$\sigma_{\lambda_{\rm NS}} \sim 130$ and $\sim 4$ for the 2G and the 3G
networks, respectively, and the 3G network can achieve $\sim 10$ times better
accuracy overall.
| [
{
"created": "Thu, 6 Oct 2022 00:00:21 GMT",
"version": "v1"
}
] | 2022-11-01 | [
[
"Cho",
"Hee-Suk",
""
]
] | The neutron star-black hole binary (NSBH) system has been considered one of the promising detection candidates for ground-based gravitational-wave (GW) detectors such as LIGO and Virgo. The tidal effects of neutron stars (NSs) are imprinted on the GW signals emitted from NSBHs as well as binary neutron stars. In this work, we study how accurately the parameter $\lambda_{\rm NS}$ can be measured in GW parameter estimation for NSBH signals. We set the parameter range for the NSBH sources to $[4M_{\odot}, 10M_{\odot}]$ for the black hole mass, $[1M_{\odot}, 2M_{\odot}]$ for the NS mass, and $[-0.9, 0.9]$ for the dimensionless black hole spin. For realistic populations of sources distributed in different parameter spaces, we calculate the measurement errors of $\lambda_{\rm NS}$ ($\sigma_{\lambda_{\rm NS}}$) using the Fisher matrix method. In particular, we perform a single-detector analysis using the advanced LIGO and the Cosmic Explorer detectors and a multi-detector analysis using the 2G (advanced LIGO-Hanford, advanced LIGO-Livingstone, advanced Virgo, and KAGRA) and the 3G (Einstein Telescope and Cosmic Explorer) networks. We show the distribution of $\sigma_{\lambda_{\rm NS}}$ for the population of sources as a one-dimensional probability density function. Our result shows that the probability density function curves are similar in shape between advanced LIGO and Cosmic Explorer, but Cosmic Explorer can achieve $\sim 15$ times better accuracy overall in the measurement of $\lambda_{\rm NS}$. In the case of the network detectors, the probability density functions are maximum at $\sigma_{\lambda_{\rm NS}} \sim 130$ and $\sim 4$ for the 2G and the 3G networks, respectively, and the 3G network can achieve $\sim 10$ times better accuracy overall. |
2005.03260 | Xisco Jim\'enez Forteza | Xisco Jim\'enez Forteza, Swetha Bhagwat, Paolo Pani, Valeria Ferrari | Spectroscopy of binary black hole ringdown using overtones and angular
modes | 18 pages, 14 figures. Version consistent with PRD | Phys. Rev. D 102, 044053 (2020) | 10.1103/PhysRevD.102.044053 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The black hole uniqueness and the no-hair theorems imply that the quasinormal
spectrum of any astrophysical black hole is determined solely by its mass and
spin. The countably infinite number of quasinormal modes of a Kerr black hole
are thus related to each other and any deviations from these relations provide
a strong hint for physics beyond the general theory of relativity. To test the
no-hair theorem using ringdown signals, it is necessary to detect at least two
quasinormal modes. In particular, one can detect the fundamental mode along
with a subdominant overtone or with another angular mode, depending on the mass
ratio and the spins of the progenitor binary. Also in the light of the recent
discovery of GW190412, studying how the mass ratio affects the prospect of
black hole spectroscopy using overtones or angular modes is pertinent, and this
is the major focus of our study. First, we provide ready-to-use fits for the
amplitudes and phases of both the angular modes and overtones as a function of
mass ratio $q\in[0,10]$. Using these fits we estimate the minimum
signal-to-noise ratio for detectability, resolvability, and measurability of
subdominant modes/tones. We find that performing black-hole spectroscopy with
angular modes is preferable when the binary mass ratio is larger than $q\approx
1.2$ (provided that the source is not located at a particularly disfavoured
inclination angle). For nonspinning, equal-mass binary black holes, the
overtones seem to be the only viable option to perform a spectroscopy test of
the no-hair theorem. However this would require a large ringdown
signal-to-noise ratio ($\approx 100$ for a $5\%$ accuracy test with two
overtones) and the inclusion of more than one overtone to reduce modelling
errors, making black-hole spectroscopy with overtones impractical in the near
future.
| [
{
"created": "Thu, 7 May 2020 05:47:34 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Aug 2020 16:26:38 GMT",
"version": "v2"
}
] | 2020-08-31 | [
[
"Forteza",
"Xisco Jiménez",
""
],
[
"Bhagwat",
"Swetha",
""
],
[
"Pani",
"Paolo",
""
],
[
"Ferrari",
"Valeria",
""
]
] | The black hole uniqueness and the no-hair theorems imply that the quasinormal spectrum of any astrophysical black hole is determined solely by its mass and spin. The countably infinite number of quasinormal modes of a Kerr black hole are thus related to each other and any deviations from these relations provide a strong hint for physics beyond the general theory of relativity. To test the no-hair theorem using ringdown signals, it is necessary to detect at least two quasinormal modes. In particular, one can detect the fundamental mode along with a subdominant overtone or with another angular mode, depending on the mass ratio and the spins of the progenitor binary. Also in the light of the recent discovery of GW190412, studying how the mass ratio affects the prospect of black hole spectroscopy using overtones or angular modes is pertinent, and this is the major focus of our study. First, we provide ready-to-use fits for the amplitudes and phases of both the angular modes and overtones as a function of mass ratio $q\in[0,10]$. Using these fits we estimate the minimum signal-to-noise ratio for detectability, resolvability, and measurability of subdominant modes/tones. We find that performing black-hole spectroscopy with angular modes is preferable when the binary mass ratio is larger than $q\approx 1.2$ (provided that the source is not located at a particularly disfavoured inclination angle). For nonspinning, equal-mass binary black holes, the overtones seem to be the only viable option to perform a spectroscopy test of the no-hair theorem. However this would require a large ringdown signal-to-noise ratio ($\approx 100$ for a $5\%$ accuracy test with two overtones) and the inclusion of more than one overtone to reduce modelling errors, making black-hole spectroscopy with overtones impractical in the near future. |
1901.03602 | Alexey Toporensky | Elena Emtsova and Alexey Toporensky | Velocities of distant objects in General Relativity revisited | 13 pages, no figures, small improvement of the text | null | 10.1134/S0202289320010053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider two most popular definitions of velocities of remote objects in
General Relativity. Our work has two motivations. From a research point of
view, we generalize the formula connecting these two velocities in FRW metrics
found by Chodorowski to arbitrary synchronous spherically symmetric metrics.
From a methodological point of view, our goal is to outline certain
counter-intuitive properties of the definitions in question, which would allow
to use them when it is reasonable and to avoid incorrect statements, based on
inappropriate use of intuition.
| [
{
"created": "Fri, 11 Jan 2019 14:51:16 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Mar 2019 13:53:26 GMT",
"version": "v2"
}
] | 2020-06-03 | [
[
"Emtsova",
"Elena",
""
],
[
"Toporensky",
"Alexey",
""
]
] | We consider two most popular definitions of velocities of remote objects in General Relativity. Our work has two motivations. From a research point of view, we generalize the formula connecting these two velocities in FRW metrics found by Chodorowski to arbitrary synchronous spherically symmetric metrics. From a methodological point of view, our goal is to outline certain counter-intuitive properties of the definitions in question, which would allow to use them when it is reasonable and to avoid incorrect statements, based on inappropriate use of intuition. |
0907.4686 | Adamantios Stavridis | Adamantios Stavridis, K. G. Arun, Clifford M. Will | Precessing supermassive black hole binaries and dark energy measurements
with LISA | 4 pages, 4 figures, version accepted to PRD | Phys.Rev.D80:067501,2009 | 10.1103/PhysRevD.80.067501 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin induced precessional modulations of gravitational wave signals from
supermassive black hole binaries can improve the estimation of luminosity
distance to the source by space based gravitational wave missions like the
Laser Interferometer Space Antenna (LISA). We study how this impacts the ablity
of LISA to do cosmology, specifically, to measure the dark energy equation of
state (EOS) parameter $w$. Using the $\Lambda$CDM model of cosmology, we show
that observations of precessing binaries by LISA, combined with a redshift
measurement, can improve the determination of $w$ up to an order of magnitude
with respect to the non precessing case depending on the masses, mass ratio and
the redshift.
| [
{
"created": "Mon, 27 Jul 2009 16:23:26 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2009 08:22:17 GMT",
"version": "v2"
}
] | 2010-03-25 | [
[
"Stavridis",
"Adamantios",
""
],
[
"Arun",
"K. G.",
""
],
[
"Will",
"Clifford M.",
""
]
] | Spin induced precessional modulations of gravitational wave signals from supermassive black hole binaries can improve the estimation of luminosity distance to the source by space based gravitational wave missions like the Laser Interferometer Space Antenna (LISA). We study how this impacts the ablity of LISA to do cosmology, specifically, to measure the dark energy equation of state (EOS) parameter $w$. Using the $\Lambda$CDM model of cosmology, we show that observations of precessing binaries by LISA, combined with a redshift measurement, can improve the determination of $w$ up to an order of magnitude with respect to the non precessing case depending on the masses, mass ratio and the redshift. |
1702.00432 | Behzad Eslam Panah | S. H. Hendi, R. B. Mann, S. Panahiyan and B. Eslam Panah | van der Waals like behaviour of topological AdS black holes in massive
gravity | 5 pages, 3 figures, Accepted for publication as a Rapid Communication
in PRD | Phys. Rev. D 95, 021501(R) (2017) | 10.1103/PhysRevD.95.021501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by recent developments in black hole thermodynamics, we investigate
van der Waals phase transitions of charged black holes in massive gravity. We
find that massive gravity theories can exhibit strikingly different
thermodynamic behaviour compared to that of Einstein gravity, and that the mass
of the graviton can generate a range of new phase transitions for topological
black holes that are otherwise forbidden.
| [
{
"created": "Wed, 1 Feb 2017 19:39:41 GMT",
"version": "v1"
}
] | 2017-02-03 | [
[
"Hendi",
"S. H.",
""
],
[
"Mann",
"R. B.",
""
],
[
"Panahiyan",
"S.",
""
],
[
"Panah",
"B. Eslam",
""
]
] | Motivated by recent developments in black hole thermodynamics, we investigate van der Waals phase transitions of charged black holes in massive gravity. We find that massive gravity theories can exhibit strikingly different thermodynamic behaviour compared to that of Einstein gravity, and that the mass of the graviton can generate a range of new phase transitions for topological black holes that are otherwise forbidden. |
1403.5669 | Julio Cesar Fabris | J.C. Fabris, O.F. Piattella, D.C. Rodrigues, M.H. Daouda | Rastall's Cosmology and its Observational Constraints | 6 pages, 5 figures, submitted to the Proceedings of the CosmoSurII
conference, Valpara\'iso, Chile, 27 - 31 May 2013 | null | 10.1063/1.4913336 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Rastall's theory is a modification of General Relativity touching one of
the cornestone of gravity theory: the conservation laws. In Rastall's theory,
the energy-momentum tensor is not conserved anymore, depending now on the
gradient of the Ricci curvature. In this sense, this theory can be seen as a
classical implementation of quantum effects in a curved background space-time.
We exploit this structure in order to reproduce some results of an effective
theory of quantum loop cosmology. Later, we propose a model for the dark sector
of the universe. In this case, the corresponding $\Lambda$CDM model appears as
the only model consistent with observational data.
| [
{
"created": "Sat, 22 Mar 2014 15:01:18 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Fabris",
"J. C.",
""
],
[
"Piattella",
"O. F.",
""
],
[
"Rodrigues",
"D. C.",
""
],
[
"Daouda",
"M. H.",
""
]
] | The Rastall's theory is a modification of General Relativity touching one of the cornestone of gravity theory: the conservation laws. In Rastall's theory, the energy-momentum tensor is not conserved anymore, depending now on the gradient of the Ricci curvature. In this sense, this theory can be seen as a classical implementation of quantum effects in a curved background space-time. We exploit this structure in order to reproduce some results of an effective theory of quantum loop cosmology. Later, we propose a model for the dark sector of the universe. In this case, the corresponding $\Lambda$CDM model appears as the only model consistent with observational data. |
2205.07784 | Andrew Coates | Andrew Coates, Fethi M. Ramazano\u{g}lu | The intrinsic pathology of self-interacting vector fields | 5+4 pages, 3+2 figures. Minor changes to bring into line with
published version | Phys. Rev. Lett. 129, 151103 (2022) | 10.1103/PhysRevLett.129.151103 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that self-interacting vector field theories exhibit unphysical
behaviour even when they are not coupled to any external field. This means any
theory featuring such vectors is in danger of being unphysical, an alarming
prospect for many proposals in cosmology, gravity, high energy physics and
beyond. The problem arises when vector fields with healthy configurations
naturally reach a point where time evolution is mathematically ill-defined. We
develop tools to easily identify this issue, and provide a simple and unifying
framework to investigate it.
| [
{
"created": "Mon, 16 May 2022 16:15:24 GMT",
"version": "v1"
},
{
"created": "Sun, 22 May 2022 15:25:59 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jun 2022 21:22:53 GMT",
"version": "v3"
},
{
"created": "Tue, 4 Oct 2022 16:47:20 GMT",
"version": "v4"
}
] | 2022-10-05 | [
[
"Coates",
"Andrew",
""
],
[
"Ramazanoğlu",
"Fethi M.",
""
]
] | We show that self-interacting vector field theories exhibit unphysical behaviour even when they are not coupled to any external field. This means any theory featuring such vectors is in danger of being unphysical, an alarming prospect for many proposals in cosmology, gravity, high energy physics and beyond. The problem arises when vector fields with healthy configurations naturally reach a point where time evolution is mathematically ill-defined. We develop tools to easily identify this issue, and provide a simple and unifying framework to investigate it. |
1208.1433 | Sumanta Chakraborty | Sumanta Chakraborty and Soumitra Sengupta | Solar system constraints on alternative gravity theories | Thoroughly revised, Matches Published Version | Phys. Rev. D 89, 026003 (2014) | 10.1103/PhysRevD.89.026003 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The perihelion precession of planetary orbits and the bending angle of null
geodesics are estimated for different gravity theories in string-inspired
models. It is shown that, for dilaton coupled gravity, the leading order
measure in the angle of bending of light comes purely from vacuum expectation
value of the dilaton field which may be interpreted as an indicator of a
dominant stringy effect over the curvature effect. We arrive at similar results
for spherically symmetric solution in quadratic gravity. We also present the
perihelion shift and bending of light in the Einstein-Maxwell-Gauss-Bonnet
theory with special reference to the Casimir effect and Damour-Polyakov
mechanism. Numerical bounds to different coupling parameters in these models
are estimated.
| [
{
"created": "Sat, 4 Aug 2012 00:54:04 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Apr 2013 06:11:06 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Jan 2014 08:55:17 GMT",
"version": "v3"
}
] | 2014-01-15 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Sengupta",
"Soumitra",
""
]
] | The perihelion precession of planetary orbits and the bending angle of null geodesics are estimated for different gravity theories in string-inspired models. It is shown that, for dilaton coupled gravity, the leading order measure in the angle of bending of light comes purely from vacuum expectation value of the dilaton field which may be interpreted as an indicator of a dominant stringy effect over the curvature effect. We arrive at similar results for spherically symmetric solution in quadratic gravity. We also present the perihelion shift and bending of light in the Einstein-Maxwell-Gauss-Bonnet theory with special reference to the Casimir effect and Damour-Polyakov mechanism. Numerical bounds to different coupling parameters in these models are estimated. |
2301.13531 | Shivaraj Kandhasamy | Junaid Yousuf and Shivaraj Kandhasamy and Manzoor A Malik | Effects of calibration uncertainties on the detection and parameter
estimation of isotropic gravitational-wave backgrounds | 11 pages, 7 figures | null | 10.1103/PhysRevD.107.102002 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational-wave backgrounds are expected to arise from the superposition
of gravitational wave signals from a large number of unresolved sources and
also from the stochastic processes that occurred in the Early universe. So far,
we have not detected any gravitational wave background, but with the
improvements in the detectors' sensitivities, such detection is expected in the
near future. The detection and inferences we draw from the search for a
gravitational-wave background will depend on the source model, the type of
search pipeline used, and the data generation in the gravitational-wave
detectors. In this work, we focus on the effect of the data generation process,
specifically the calibration of the detectors' digital output into strain data
used by the search pipelines. Using the calibration model of the current LIGO
detectors as an example, we show that for power-law source models and
calibration uncertainties $\lesssim 10 \%$, the detection of isotropic
gravitational wave background is not significantly affected. We also show that
the source parameter estimation and upper limits calculations get biased. For
calibration uncertainties of $\lesssim 5 \%$, the biases are not significant
($\lesssim 2 \%$), but for larger calibration uncertainties, they might become
significant, especially when trying to differentiate between different models
of isotropic gravitational-wave backgrounds.
| [
{
"created": "Tue, 31 Jan 2023 10:25:57 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2023 11:18:22 GMT",
"version": "v2"
}
] | 2023-05-17 | [
[
"Yousuf",
"Junaid",
""
],
[
"Kandhasamy",
"Shivaraj",
""
],
[
"Malik",
"Manzoor A",
""
]
] | Gravitational-wave backgrounds are expected to arise from the superposition of gravitational wave signals from a large number of unresolved sources and also from the stochastic processes that occurred in the Early universe. So far, we have not detected any gravitational wave background, but with the improvements in the detectors' sensitivities, such detection is expected in the near future. The detection and inferences we draw from the search for a gravitational-wave background will depend on the source model, the type of search pipeline used, and the data generation in the gravitational-wave detectors. In this work, we focus on the effect of the data generation process, specifically the calibration of the detectors' digital output into strain data used by the search pipelines. Using the calibration model of the current LIGO detectors as an example, we show that for power-law source models and calibration uncertainties $\lesssim 10 \%$, the detection of isotropic gravitational wave background is not significantly affected. We also show that the source parameter estimation and upper limits calculations get biased. For calibration uncertainties of $\lesssim 5 \%$, the biases are not significant ($\lesssim 2 \%$), but for larger calibration uncertainties, they might become significant, especially when trying to differentiate between different models of isotropic gravitational-wave backgrounds. |
2008.00945 | Thomas Celora | Thomas Celora, Nils Andersson and Greg L. Comer | Linearizing a Non-linear Formulation for General Relativistic
Dissipative Fluids | Final version as published on Classical and Quantum Gravity | null | 10.1088/1361-6382/abd7c1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fully non-linear equations of motion for dissipative general relativistic
multi-fluids can be obtained from an action principle involving the explicit
use of lower dimensional matter spaces. More traditional strategies for
incorporating dissipation-like the famous Mueller-Israel-Stewart model-are
based on expansions away from equilibrium defined, in part, by the laws of
thermodynamics. The goal here is to build a formalism to facilitate comparison
of the action-based results with those based on the traditional approach. The
first step of the process is to use the action-based approach itself to
construct self-consistent notions of equilibrium. Next, first-order deviations
are developed directly on the matter spaces, which motivates the latter as the
natural arena for the underlying thermodynamics. Finally, we identify the
dissipation terms of the action-based model with first-order "thermodynamical"
fluxes, on which the traditional models are built. The description is developed
in a general setting so that the formalism can be used to describe multi-fluid
systems, for which causal and stable models are not yet available. As an
illustration of the approach, a simple application of a single viscous fluid is
considered and, even though the expansion is halted at first order, we sketch
how a causal response can be implemented through Cattaneo-type equations.
| [
{
"created": "Mon, 3 Aug 2020 15:25:34 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 2021 15:10:31 GMT",
"version": "v2"
}
] | 2021-01-13 | [
[
"Celora",
"Thomas",
""
],
[
"Andersson",
"Nils",
""
],
[
"Comer",
"Greg L.",
""
]
] | Fully non-linear equations of motion for dissipative general relativistic multi-fluids can be obtained from an action principle involving the explicit use of lower dimensional matter spaces. More traditional strategies for incorporating dissipation-like the famous Mueller-Israel-Stewart model-are based on expansions away from equilibrium defined, in part, by the laws of thermodynamics. The goal here is to build a formalism to facilitate comparison of the action-based results with those based on the traditional approach. The first step of the process is to use the action-based approach itself to construct self-consistent notions of equilibrium. Next, first-order deviations are developed directly on the matter spaces, which motivates the latter as the natural arena for the underlying thermodynamics. Finally, we identify the dissipation terms of the action-based model with first-order "thermodynamical" fluxes, on which the traditional models are built. The description is developed in a general setting so that the formalism can be used to describe multi-fluid systems, for which causal and stable models are not yet available. As an illustration of the approach, a simple application of a single viscous fluid is considered and, even though the expansion is halted at first order, we sketch how a causal response can be implemented through Cattaneo-type equations. |
1209.2979 | Julio Cesar Fabris | J.C. Fabris, G.T. Marques | Hawking radiation for non asymptotically flat dilatonic black holes
using gravitational anomaly | Latex file, 22 pages. Some discussions enlarged. New references.
Accepted for publication in the European Physical Journal C | null | 10.1140/epjc/s10052-012-2214-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The $d$-dimensional scalar field action may be reduced, in the background
geometry of a black hole, to a 2-dimensional effective action. In the near
horizon region, it appears a gravitational anomaly: the energy-momentum tensor
of the scalar field is not conserved anymore. This anomaly is removed by
introducing a term related to the Hawking temperature of the black hole. Even
if the temperature term introduced is not covariant, a gauge transformation may
restore the covariance. We apply this method to compute the temperature of the
black hole of the dilatonic non asymptotically flat black holes. We compare the
results with those obtained through other methods.
| [
{
"created": "Thu, 13 Sep 2012 18:06:53 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Oct 2012 14:48:49 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Fabris",
"J. C.",
""
],
[
"Marques",
"G. T.",
""
]
] | The $d$-dimensional scalar field action may be reduced, in the background geometry of a black hole, to a 2-dimensional effective action. In the near horizon region, it appears a gravitational anomaly: the energy-momentum tensor of the scalar field is not conserved anymore. This anomaly is removed by introducing a term related to the Hawking temperature of the black hole. Even if the temperature term introduced is not covariant, a gauge transformation may restore the covariance. We apply this method to compute the temperature of the black hole of the dilatonic non asymptotically flat black holes. We compare the results with those obtained through other methods. |
2305.04360 | H{\aa}kan Andr\'easson | E. Ames, H. Andr\'easson and O. Rinne | On the Hoop conjecture and the weak cosmic censorship conjecture for the
axisymmetric Einstein-Vlasov system | 18 pages, 7 figures | Phys. Rev. D 108, 064054 (2023) | 10.1103/PhysRevD.108.064054 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider gravitational collapse for the axially symmetric Einstein-Vlasov
system. We investigate the weak cosmic censorship conjecture in the case of
highly prolate initial data and we investigate the ``only if" part of the Hoop
conjecture. Shapiro and Teukolsky initiated a similar study in 1991
\cite{Shapiro1991} where they found support that the weak cosmic censorship
conjecture was violated for sufficiently prolate spheroidal initial data. More
recently, independent studies of this problem have been carried out by Yoo,
Harada and Okawa \cite{Yoo2017} and by East \cite{East2019}. A common feature
in these works is that the initial data are dust-like. Dust can be considered
as a \textit{singular} case of matter described by the Einstein-Vlasov system.
The original motivation by Shapiro and Teukolsky to study this problem is based
on the Lin-Mestel-Shu instability for gravitational collapse of uniform
spheroids in the case of dust in Newtonian gravity. We argue that the
Lin-Mestel-Shu solution is not relevant for studying the weak cosmic censorship
of the Einstein-Vlasov system and we argue that dust-like initial data is also
not relevant. To investigate collapse of highly prolate spheroidal
configurations for the Einstein-Vlasov system is nevertheless interesting in
view of the Hoop conjecture. By choosing highly prolate initial data the weak
cosmic censorship conjecture is seriously tested. We carry out such a study for
initial data which are not dust-like. We find formation of an apparent horizon
in all cases we consider, which provides support for the weak cosmic censorship
conjecture. In our tests of the Hoop conjecture we compute the polar
circumference $\mathcal{C}_{H,p}$ at the time when the apparent horizon forms
and find that it is less than 12% above $4\pi M$, where $M$ is the irreducible
mass of the apparent horizon, which agrees with the spirit of the Hoop
conjecture.
| [
{
"created": "Sun, 7 May 2023 19:38:23 GMT",
"version": "v1"
}
] | 2024-02-19 | [
[
"Ames",
"E.",
""
],
[
"Andréasson",
"H.",
""
],
[
"Rinne",
"O.",
""
]
] | We consider gravitational collapse for the axially symmetric Einstein-Vlasov system. We investigate the weak cosmic censorship conjecture in the case of highly prolate initial data and we investigate the ``only if" part of the Hoop conjecture. Shapiro and Teukolsky initiated a similar study in 1991 \cite{Shapiro1991} where they found support that the weak cosmic censorship conjecture was violated for sufficiently prolate spheroidal initial data. More recently, independent studies of this problem have been carried out by Yoo, Harada and Okawa \cite{Yoo2017} and by East \cite{East2019}. A common feature in these works is that the initial data are dust-like. Dust can be considered as a \textit{singular} case of matter described by the Einstein-Vlasov system. The original motivation by Shapiro and Teukolsky to study this problem is based on the Lin-Mestel-Shu instability for gravitational collapse of uniform spheroids in the case of dust in Newtonian gravity. We argue that the Lin-Mestel-Shu solution is not relevant for studying the weak cosmic censorship of the Einstein-Vlasov system and we argue that dust-like initial data is also not relevant. To investigate collapse of highly prolate spheroidal configurations for the Einstein-Vlasov system is nevertheless interesting in view of the Hoop conjecture. By choosing highly prolate initial data the weak cosmic censorship conjecture is seriously tested. We carry out such a study for initial data which are not dust-like. We find formation of an apparent horizon in all cases we consider, which provides support for the weak cosmic censorship conjecture. In our tests of the Hoop conjecture we compute the polar circumference $\mathcal{C}_{H,p}$ at the time when the apparent horizon forms and find that it is less than 12% above $4\pi M$, where $M$ is the irreducible mass of the apparent horizon, which agrees with the spirit of the Hoop conjecture. |
1510.06981 | Nelson Videla Dr. | Grigorios Panotopoulos and Nelson Videla | Warm $\frac{\lambda}{4}\phi^{4}$ inflationary universe model in light of
Planck 2015 results | 16 pages, 2 figures. Accepted for publication in EPJC | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we show that warm chaotic inflation characterized by a
simple $\frac{\lambda}{4}\phi^{4}$ self-interaction potential for the inflaton,
excluded by current data in standard cold inflation, and by an inflaton decay
rate proportional to the temperature, is in agreement with the latest Planck
data. The parameters of the model are constrained, and our results show that
the model predicts a negligible tensor-to-scalar ratio in the strong
dissipative regime, while in the weak dissipative regime the tensor-to-scalar
ratio can be large enough to be observed.
| [
{
"created": "Fri, 23 Oct 2015 16:13:28 GMT",
"version": "v1"
}
] | 2015-10-26 | [
[
"Panotopoulos",
"Grigorios",
""
],
[
"Videla",
"Nelson",
""
]
] | In the present work we show that warm chaotic inflation characterized by a simple $\frac{\lambda}{4}\phi^{4}$ self-interaction potential for the inflaton, excluded by current data in standard cold inflation, and by an inflaton decay rate proportional to the temperature, is in agreement with the latest Planck data. The parameters of the model are constrained, and our results show that the model predicts a negligible tensor-to-scalar ratio in the strong dissipative regime, while in the weak dissipative regime the tensor-to-scalar ratio can be large enough to be observed. |
2304.08676 | Bo-Qiang Ma | Jie Zhu, Bo-Qiang Ma | Trajectories of astroparticles in pseudo-Finsler spacetime with the most
general modified dispersion | 9 pages, no figure, version for journal publication. arXiv admin
note: text overlap with arXiv:2206.07616 | Eur. Phys. J. C 83 (2023) 349 | 10.1140/epjc/s10052-023-11517-8 | null | gr-qc astro-ph.HE hep-ph math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Finsler geometry is a natural and fundamental generalization of Riemann
geometry, and is a tool to research Lorentz invariance violation. We find the
connection between the most general modified dispersion relation and a
pseudo-Finsler structure, and then we calculate the arrival time delay of
astroparticles with different modified dispersion relations in the framework of
Finsler geometry. The result suggests that the time delay is irrelevant with
the exact form of the modified dispersion relation. If the modified term
becomes 0 when $E=p$, there is no arrival time difference, otherwise the time
delays only depend on the Lorentz violation scale and the order at which the
Lorentz invariance breaks.
| [
{
"created": "Tue, 18 Apr 2023 00:58:18 GMT",
"version": "v1"
},
{
"created": "Mon, 1 May 2023 07:49:50 GMT",
"version": "v2"
}
] | 2023-05-02 | [
[
"Zhu",
"Jie",
""
],
[
"Ma",
"Bo-Qiang",
""
]
] | Finsler geometry is a natural and fundamental generalization of Riemann geometry, and is a tool to research Lorentz invariance violation. We find the connection between the most general modified dispersion relation and a pseudo-Finsler structure, and then we calculate the arrival time delay of astroparticles with different modified dispersion relations in the framework of Finsler geometry. The result suggests that the time delay is irrelevant with the exact form of the modified dispersion relation. If the modified term becomes 0 when $E=p$, there is no arrival time difference, otherwise the time delays only depend on the Lorentz violation scale and the order at which the Lorentz invariance breaks. |
1903.08435 | Mudassar Sabir | Mudassar Sabir, Waqas Ahmed, Yungui Gong and Yizhou Lu | $\alpha$-attractor from superconformal E-models in brane inflation | 11 pages, 3 figures | Eur. Phys. J. C 80, 15 (2020) | 10.1140/epjc/s10052-019-7589-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the large extra dimensional braneworld inflation, Friedmann equation is
modified to include a quadratic term in energy density with an additional
parameter $\lambda$ called brane tension in addition to the usual linear term.
The high energy brane corrections modify the slow-roll parameters and affect
the behaviour of inflation. We analyse the superconformal inflation for
E-models and find that there exist $\alpha$-attractors in brane inflation. The
predictions for the scalar spectral index $n_s$ and the tensor-to-scalar ratio
$r$ are computed numerically, and approximate analytic formulas in the high
energy limit have been given for the observable $n_s$ and $r$. The constraints
on the model parameters are obtained by using Planck 2018 and BICEP2
observational data.
| [
{
"created": "Wed, 20 Mar 2019 11:00:18 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jan 2020 13:13:44 GMT",
"version": "v2"
}
] | 2020-01-15 | [
[
"Sabir",
"Mudassar",
""
],
[
"Ahmed",
"Waqas",
""
],
[
"Gong",
"Yungui",
""
],
[
"Lu",
"Yizhou",
""
]
] | In the large extra dimensional braneworld inflation, Friedmann equation is modified to include a quadratic term in energy density with an additional parameter $\lambda$ called brane tension in addition to the usual linear term. The high energy brane corrections modify the slow-roll parameters and affect the behaviour of inflation. We analyse the superconformal inflation for E-models and find that there exist $\alpha$-attractors in brane inflation. The predictions for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ are computed numerically, and approximate analytic formulas in the high energy limit have been given for the observable $n_s$ and $r$. The constraints on the model parameters are obtained by using Planck 2018 and BICEP2 observational data. |
1908.03349 | Titus K Mathew | Hareesh T, P.B. Krishna and Titus K Mathew | First Law of Thermodynamics and Emergence of Cosmic Space in a Non-Flat
Universe | 17 pages | null | 10.1088/1475-7516/2019/12/024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The emergence of cosmic space as cosmic time progresses is an exciting idea
advanced by Padmanabhan to explain the accelerated expansion of the universe.
The generalization of Padmanabhan's conjecture to the non-flat universe has
resulted in scepticism about the choice of volume such that the law of
emergence can not be appropriately formulated if one uses proper invariant
volume. The deep connection between the first law of thermodynamics and the law
of emergence \cite{mahith}, motivate us to explore the status of the first law
in a non-flat universe when one uses proper invariant volume. We have shown
that the first law of thermodynamics, $dE = TdS +WdV$ cannot be formulated
properly for a non-flat universe using proper invariant volume. We have also
investigated the status of the first law of the form $-dE = TdS$ in a non-flat
universe. We have shown that the energy change dE within the horizon and the
outward energy flux are not equivalent to each other in a non-flat universe
when we use the proper invariant volume. We have further shown that the
consistency between the above two forms of the first law claimed in Ref.
\cite{caiakb} will hold only with the use of the areal volume of the horizon.
Thus, a consistent formulation of the above two forms of the first law of
thermodynamics demands the use of areal volume.
| [
{
"created": "Fri, 9 Aug 2019 07:43:40 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Sep 2019 11:52:02 GMT",
"version": "v2"
}
] | 2019-12-18 | [
[
"T",
"Hareesh",
""
],
[
"Krishna",
"P. B.",
""
],
[
"Mathew",
"Titus K",
""
]
] | The emergence of cosmic space as cosmic time progresses is an exciting idea advanced by Padmanabhan to explain the accelerated expansion of the universe. The generalization of Padmanabhan's conjecture to the non-flat universe has resulted in scepticism about the choice of volume such that the law of emergence can not be appropriately formulated if one uses proper invariant volume. The deep connection between the first law of thermodynamics and the law of emergence \cite{mahith}, motivate us to explore the status of the first law in a non-flat universe when one uses proper invariant volume. We have shown that the first law of thermodynamics, $dE = TdS +WdV$ cannot be formulated properly for a non-flat universe using proper invariant volume. We have also investigated the status of the first law of the form $-dE = TdS$ in a non-flat universe. We have shown that the energy change dE within the horizon and the outward energy flux are not equivalent to each other in a non-flat universe when we use the proper invariant volume. We have further shown that the consistency between the above two forms of the first law claimed in Ref. \cite{caiakb} will hold only with the use of the areal volume of the horizon. Thus, a consistent formulation of the above two forms of the first law of thermodynamics demands the use of areal volume. |
2302.00584 | Giacomo Pollari | Pollari Giacomo | A Nieh-Yan-like topological invariant in General Relativity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present work we will introduce and prove a topological invariant term
in General Relativity involving the torsion tensor that has never been showed
before. Such a term is a slight modification of the Nieh-Yan four-form and
likewise it stems from a Chern-Simons three-form. We provide the proof in both
holonomic and orthogonal basis and show that its integral reduces to a boundary
term that vanishes with the right conditions. As all topological invariant
objects the new term does not affect the Einstein field equations in pure
gravity, but when matter fields couple to the gravitational field, the torsion
tensor arises and its contribution changes the "rules of the game". Therefore
it is of great importance to study how those pieces irrelevant in bare gravity
modify the interaction with fields of the Standard Model.
| [
{
"created": "Wed, 1 Feb 2023 16:57:42 GMT",
"version": "v1"
}
] | 2023-02-02 | [
[
"Giacomo",
"Pollari",
""
]
] | In the present work we will introduce and prove a topological invariant term in General Relativity involving the torsion tensor that has never been showed before. Such a term is a slight modification of the Nieh-Yan four-form and likewise it stems from a Chern-Simons three-form. We provide the proof in both holonomic and orthogonal basis and show that its integral reduces to a boundary term that vanishes with the right conditions. As all topological invariant objects the new term does not affect the Einstein field equations in pure gravity, but when matter fields couple to the gravitational field, the torsion tensor arises and its contribution changes the "rules of the game". Therefore it is of great importance to study how those pieces irrelevant in bare gravity modify the interaction with fields of the Standard Model. |
1112.6215 | Raf Guedens | Raf Guedens, Ted Jacobson and Sudipta Sarkar | Horizon entropy and higher curvature equations of state | 16 pages, 3 figures; minor improvements to presentation | null | 10.1103/PhysRevD.85.064017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Clausius relation between entropy change and heat flux has previously
been used to derive Einstein's field equations as an equation of state. In that
derivation the entropy is proportional to the area of a local causal horizon,
and the heat is the energy flux across the horizon, defined relative to an
approximate boost Killing vector. We examine here whether a similar derivation
can be given for extensions beyond Einstein gravity to include higher
derivative and higher curvature terms. We review previous proposals which, in
our opinion, are problematic or incomplete. Refining one of these, we assume
that the horizon entropy depends on an approximate local Killing vector in a
way that mimics the diffeomorphism Noether charge that yields the entropy of a
stationary black hole. We show how this can be made to work if various
restrictions are imposed on the nature of the horizon slices and the
approximate Killing vector. Also, an integrability condition on the assumed
horizon entropy density must hold. This can yield field equations of a
Lagrangian constructed algebraically from the metric and Riemann tensor, but
appears unlikely to allow for derivatives of curvature in the Lagrangian.
| [
{
"created": "Thu, 29 Dec 2011 01:55:07 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2012 23:02:10 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Guedens",
"Raf",
""
],
[
"Jacobson",
"Ted",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | The Clausius relation between entropy change and heat flux has previously been used to derive Einstein's field equations as an equation of state. In that derivation the entropy is proportional to the area of a local causal horizon, and the heat is the energy flux across the horizon, defined relative to an approximate boost Killing vector. We examine here whether a similar derivation can be given for extensions beyond Einstein gravity to include higher derivative and higher curvature terms. We review previous proposals which, in our opinion, are problematic or incomplete. Refining one of these, we assume that the horizon entropy depends on an approximate local Killing vector in a way that mimics the diffeomorphism Noether charge that yields the entropy of a stationary black hole. We show how this can be made to work if various restrictions are imposed on the nature of the horizon slices and the approximate Killing vector. Also, an integrability condition on the assumed horizon entropy density must hold. This can yield field equations of a Lagrangian constructed algebraically from the metric and Riemann tensor, but appears unlikely to allow for derivatives of curvature in the Lagrangian. |
2212.07018 | Sajal Mukherjee | Sajal Mukherjee and Sumanta Chakraborty | Transition from inspiral to plunge for braneworld EMRI | 22 pages, 2 figures | Class. Quantum Grav. 40, 145013 (2023) | 10.1088/1361-6382/acdd47 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present article, we discuss the late inspiral and then the transition
regime to the plunge phase of a secondary, less massive compact object into a
more massive braneworld black hole, in the context of an extreme-mass-ratio
inspiral. We obtain the approximate expressions for fluxes due to slowly
evolving constants of motion, such as the energy and the angular momentum, in
the presence of the tidal charge inherited from the higher spacetime dimensions
for an extreme-mass-ratio system. These expressions for fluxes are further used
to introduce dissipative effects while modeling the inspiral to the plunge
phase through the transition regime. Within our setup, we provide a qualitative
understanding of how the additional tidal charge present in the braneworld
scenario may affect the timescale of the late inspiral to the plunge, in
particular, by enhancing the time scale of the transition regime. Finally, we
provide an estimate for the tidal charge from the higher dimensions, using the
observable aspects of the transition regime from the late inspiral to the
plunge by the gravitational wave detectors.
| [
{
"created": "Wed, 14 Dec 2022 04:13:41 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2023 05:40:18 GMT",
"version": "v2"
}
] | 2023-06-29 | [
[
"Mukherjee",
"Sajal",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | In the present article, we discuss the late inspiral and then the transition regime to the plunge phase of a secondary, less massive compact object into a more massive braneworld black hole, in the context of an extreme-mass-ratio inspiral. We obtain the approximate expressions for fluxes due to slowly evolving constants of motion, such as the energy and the angular momentum, in the presence of the tidal charge inherited from the higher spacetime dimensions for an extreme-mass-ratio system. These expressions for fluxes are further used to introduce dissipative effects while modeling the inspiral to the plunge phase through the transition regime. Within our setup, we provide a qualitative understanding of how the additional tidal charge present in the braneworld scenario may affect the timescale of the late inspiral to the plunge, in particular, by enhancing the time scale of the transition regime. Finally, we provide an estimate for the tidal charge from the higher dimensions, using the observable aspects of the transition regime from the late inspiral to the plunge by the gravitational wave detectors. |
1811.11799 | Eugen Radu | C. Herdeiro, I. Perapechka, E. Radu and Ya. Shnir | Gravitating solitons and black holes with synchronised hair in the four
dimensional O(3) sigma-model | 24 pages, 7 figures | J. High Energ. Phys. (2019) 2019: 111 | 10.1007/JHEP02(2019)111 | DIAS-STP-18-17 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the $\mathrm{O}(3)$ non-linear sigma-model, composed of three
real scalar fields with a standard kinetic term and with a symmetry breaking
potential in four spacetime dimensions. We show that this simple, geometrically
motivated model, admits both self-gravitating, asymptotically flat,
non-topological solitons and hairy black holes, when minimally coupled to
Einstein's gravity, $without$ the need to introduce higher order kinetic terms
in the scalar fields action. Both spherically symmetric and spinning, axially
symmetric solutions are studied. The solutions are obtained under a ansatz with
oscillation (in the static case) or rotation (in the spinning case) in the
internal space. Thus, there is symmetry non-inheritance: the matter sector is
not invariant under the individual spacetime isometries. For the hairy black
holes, which are necessarily spinning, the internal rotation (isorotation) must
be synchronous with the rotational angular velocity of the event horizon. We
explore the domain of existence of the solutions and some of their physical
properties, that resemble closely those of (mini) boson stars and Kerr black
holes with synchronised scalar hair in Einstein-(massive, complex)-Klein-Gordon
theory.
| [
{
"created": "Wed, 28 Nov 2018 19:47:48 GMT",
"version": "v1"
}
] | 2019-05-02 | [
[
"Herdeiro",
"C.",
""
],
[
"Perapechka",
"I.",
""
],
[
"Radu",
"E.",
""
],
[
"Shnir",
"Ya.",
""
]
] | We consider the $\mathrm{O}(3)$ non-linear sigma-model, composed of three real scalar fields with a standard kinetic term and with a symmetry breaking potential in four spacetime dimensions. We show that this simple, geometrically motivated model, admits both self-gravitating, asymptotically flat, non-topological solitons and hairy black holes, when minimally coupled to Einstein's gravity, $without$ the need to introduce higher order kinetic terms in the scalar fields action. Both spherically symmetric and spinning, axially symmetric solutions are studied. The solutions are obtained under a ansatz with oscillation (in the static case) or rotation (in the spinning case) in the internal space. Thus, there is symmetry non-inheritance: the matter sector is not invariant under the individual spacetime isometries. For the hairy black holes, which are necessarily spinning, the internal rotation (isorotation) must be synchronous with the rotational angular velocity of the event horizon. We explore the domain of existence of the solutions and some of their physical properties, that resemble closely those of (mini) boson stars and Kerr black holes with synchronised scalar hair in Einstein-(massive, complex)-Klein-Gordon theory. |
1902.04859 | C. Q. Geng | Chao-Qiang Geng, Wei-Cheng Hsu, Jhih-Rong Lu and Ling-Wei Luo | Thermodynamics of $f(R)$ Gravity with Disformal Transformation | 23 pages, no figure, published version in Entropy 21, 172 (2019) | Entropy 21, 172 (2019) | 10.3390/e21020172 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study thermodynamics in $f(R)$ gravity with the disformal transformation.
The transformation applied to the matter Lagrangian has the form of $\g_{\m\n}
= A(\phi,X)g_{\m\n} + B(\phi,X)\pa_\m\f\pa_\n\f$ with the assumption of the
Minkowski matter metric $\g_{\m\n} = \e_{\m\n}$, where $\phi$ is the disformal
scalar and $X$ is the corresponding kinetic term of $\phi$. We verify the
generalized first and second laws of thermodynamics in this disformal type of
$f(R)$ gravity in the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe.
In addition, we show that the Hubble parameter contains the disformally induced
terms, which define the effectively varying equations of state for matter.
| [
{
"created": "Wed, 13 Feb 2019 11:00:50 GMT",
"version": "v1"
}
] | 2019-02-14 | [
[
"Geng",
"Chao-Qiang",
""
],
[
"Hsu",
"Wei-Cheng",
""
],
[
"Lu",
"Jhih-Rong",
""
],
[
"Luo",
"Ling-Wei",
""
]
] | We study thermodynamics in $f(R)$ gravity with the disformal transformation. The transformation applied to the matter Lagrangian has the form of $\g_{\m\n} = A(\phi,X)g_{\m\n} + B(\phi,X)\pa_\m\f\pa_\n\f$ with the assumption of the Minkowski matter metric $\g_{\m\n} = \e_{\m\n}$, where $\phi$ is the disformal scalar and $X$ is the corresponding kinetic term of $\phi$. We verify the generalized first and second laws of thermodynamics in this disformal type of $f(R)$ gravity in the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. In addition, we show that the Hubble parameter contains the disformally induced terms, which define the effectively varying equations of state for matter. |
1911.06990 | Zahra Haghani | Zahra Haghani | Cosmology of the non-local Proca theory | 10 pages, 2 figures | Phys.Dark Univ. 32 (2021) 100817 | 10.1016/j.dark.2021.100817 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we will consider cosmological implications of the Maxwell
theory coupled to a non-local $U(1)$-symmetric term. It is well-known that the
theory in flat space time, reduces to the Proca theory. However, it will be
shown that in curved space time the resulting theory will differ from the
coupled Einstein-Proca system. The cosmological perturbations on top of the de
Sitter space-time is also considered and the dynamics of separate modes will be
investigated in detail. Anisotropic cosmology of the model is also investigated
and we will show that the behavior of the universe at late time satisfies the
observational data and the model predicts an isotropic universe.
| [
{
"created": "Sat, 16 Nov 2019 08:23:24 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Nov 2019 07:02:06 GMT",
"version": "v2"
},
{
"created": "Fri, 23 Apr 2021 08:21:42 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Apr 2022 10:43:46 GMT",
"version": "v4"
}
] | 2022-04-18 | [
[
"Haghani",
"Zahra",
""
]
] | In this paper, we will consider cosmological implications of the Maxwell theory coupled to a non-local $U(1)$-symmetric term. It is well-known that the theory in flat space time, reduces to the Proca theory. However, it will be shown that in curved space time the resulting theory will differ from the coupled Einstein-Proca system. The cosmological perturbations on top of the de Sitter space-time is also considered and the dynamics of separate modes will be investigated in detail. Anisotropic cosmology of the model is also investigated and we will show that the behavior of the universe at late time satisfies the observational data and the model predicts an isotropic universe. |
1911.01422 | Artyom Astashenok V | Artyom V. Astashenok, Alexander S. Tepliakov | Some models of holographic dark energy on the Randall-Sundrum brane and
observational data | 12 pp., 5 figs., 3 tables, accepted in Int. J. Mod. Phys. D | null | 10.1142/S0218271819501761 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The some models of holographic dark energy for Randall-Sandrum brane are
considered. For first class of dark energy models we take energy density in
form $\sim L^{2\gamma-4}$ where $L$ is size of events horizon in Universe and
$\gamma$ is parameter (Tsallis holographic energy). Analysis of observational
data allows to define upper limit on value of $\delta=\rho_{0}/2\lambda$
($\rho_{0}$ is current energy density in the Universe and $\lambda$ is brane
tension). Then we investigate models for which dark energy density has form
$\rho_{de}=C^{2}L^{-2}-C_{1}^{2}H^{2}$ where $H$ is Hubble parameter.
| [
{
"created": "Mon, 4 Nov 2019 14:50:02 GMT",
"version": "v1"
}
] | 2020-03-18 | [
[
"Astashenok",
"Artyom V.",
""
],
[
"Tepliakov",
"Alexander S.",
""
]
] | The some models of holographic dark energy for Randall-Sandrum brane are considered. For first class of dark energy models we take energy density in form $\sim L^{2\gamma-4}$ where $L$ is size of events horizon in Universe and $\gamma$ is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of $\delta=\rho_{0}/2\lambda$ ($\rho_{0}$ is current energy density in the Universe and $\lambda$ is brane tension). Then we investigate models for which dark energy density has form $\rho_{de}=C^{2}L^{-2}-C_{1}^{2}H^{2}$ where $H$ is Hubble parameter. |
2404.14335 | David Kubiznak | David Kubiznak, Otakar Sv\'itek, Tayebeh Tahamtan | Regularized Conformal Electrodynamics: Novel C-metric in (2+1)
Dimensions | 10 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conformal electrodynamics is a particularly interesting example of power
Maxwell non-linear electrodynamics, designed to possess conformal symmetry in
all dimensions. In this paper, we propose a regularized version of Conformal
electrodynamics, minimally regularizing the field of a point charge at the
origin by breaking the conformal invariance of the theory with a dimensionfull
"Born-Infeld-like" parameter. In four dimensions the new theory reduces to the
recently studied Regularized Maxwell electrodynamics, distinguished by its
"Maxwell-like" solutions for accelerated and slowly rotating black hole
spacetimes. Focusing on three dimensions, we show that the new theory shares
many of the properties of its four-dimensional cousin, including the existence
of the charged C-metric solution (currently unknown in the Maxwell theory).
| [
{
"created": "Mon, 22 Apr 2024 16:52:34 GMT",
"version": "v1"
}
] | 2024-04-23 | [
[
"Kubiznak",
"David",
""
],
[
"Svítek",
"Otakar",
""
],
[
"Tahamtan",
"Tayebeh",
""
]
] | Conformal electrodynamics is a particularly interesting example of power Maxwell non-linear electrodynamics, designed to possess conformal symmetry in all dimensions. In this paper, we propose a regularized version of Conformal electrodynamics, minimally regularizing the field of a point charge at the origin by breaking the conformal invariance of the theory with a dimensionfull "Born-Infeld-like" parameter. In four dimensions the new theory reduces to the recently studied Regularized Maxwell electrodynamics, distinguished by its "Maxwell-like" solutions for accelerated and slowly rotating black hole spacetimes. Focusing on three dimensions, we show that the new theory shares many of the properties of its four-dimensional cousin, including the existence of the charged C-metric solution (currently unknown in the Maxwell theory). |
1311.3053 | Liu Zhao | Wei Xu, Hao Xu and Liu Zhao | Gauss-Bonnet coupling constant as a free thermodynamical variable and
the associated criticality | 23 pages. V2: modified all P_{GB}-r_+ plots using dimensionless
variables, added comments on the relationship to Einstein limit | Eur. Phys. J. C (2014) 74:2970 | 10.1140/epjc/s10052-014-2970-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamic phase space of Gauss-Bonnet (GB) AdS black holes is
extended, taking the inverse of the GB coupling constant as a new thermodynamic
pressure $P_{\mathrm{GB}}$. We studied the critical behavior associated with
$P_{\mathrm{GB}}$ in the extended thermodynamic phase space at fixed
cosmological constant and electric charge. The result shows that when the black
holes are neutral, the associated critical points can only exist in five
dimensional GB-AdS black holes with spherical topology, and the corresponding
critical exponents are identical to those for Van der Waals system. For charged
GB-AdS black holes, it is shown that there can be only one critical point in
five dimensions (for black holes with either spherical or hyperbolic
topologies), which also requires the electric charge to be bounded within some
appropriate range; while in $d>5$ dimensions, there can be up to two different
critical points at the same electric charge, and the phase transition can occur
only at temperatures which are not in between the two critical values.
| [
{
"created": "Wed, 13 Nov 2013 09:20:18 GMT",
"version": "v1"
},
{
"created": "Mon, 12 May 2014 07:11:44 GMT",
"version": "v2"
}
] | 2014-08-19 | [
[
"Xu",
"Wei",
""
],
[
"Xu",
"Hao",
""
],
[
"Zhao",
"Liu",
""
]
] | The thermodynamic phase space of Gauss-Bonnet (GB) AdS black holes is extended, taking the inverse of the GB coupling constant as a new thermodynamic pressure $P_{\mathrm{GB}}$. We studied the critical behavior associated with $P_{\mathrm{GB}}$ in the extended thermodynamic phase space at fixed cosmological constant and electric charge. The result shows that when the black holes are neutral, the associated critical points can only exist in five dimensional GB-AdS black holes with spherical topology, and the corresponding critical exponents are identical to those for Van der Waals system. For charged GB-AdS black holes, it is shown that there can be only one critical point in five dimensions (for black holes with either spherical or hyperbolic topologies), which also requires the electric charge to be bounded within some appropriate range; while in $d>5$ dimensions, there can be up to two different critical points at the same electric charge, and the phase transition can occur only at temperatures which are not in between the two critical values. |
gr-qc/0412114 | C\'edric Deffayet | Cedric Deffayet | Cosmological perturbations of brane-induced gravity and the vDVZ
discontinuity on FLRW space-times | 36 pages, v.2, typos corrected | Phys.Rev.D71:103501,2005 | 10.1103/PhysRevD.71.103501 | null | gr-qc astro-ph hep-th | null | We investigate the cosmological perturbations of the brane-induced
(Dvali-Gabadadze-Porrati) model which exhibits a van Dam-Veltman-Zakharov
(vDVZ) discontinuity when linearized over a Minkowski background. We show that
the linear brane scalar cosmological perturbations over an arbitrary
Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time have a well defined limit
when the radius of transition between 4D and 5D gravity is sent to infinity
with respect to the background Hubble radius. This radius of transition plays
for the brane-induced gravity model a role equivalent to the Compton wavelength
of the graviton in a Pauli-Fierz theory, as far as the vDVZ discontinuity is
concerned. This well defined limit is shown to obey the linearized 4D
Einstein's equations whenever the Hubble factor is non vanishing. This shows
the disappearance of the vDVZ discontinuity for general FLRW background, and
extends the previously know result for maximally-symmetric space-times of non
vanishing curvature. Our reasoning is valid for matter with simple equation of
state such as a scalar field, or a perfect fluid with adiabatic perturbations,
and involves to distinguish between space-times with a vanishing scalar
curvature and space-times with a non vanishing one. We also discuss the
validity of the linear perturbation theory, in particular for those FLRW
space-times where the Ricci scalar is vanishing only on a set of zero measure.
In those cases, we argue that the linear perturbation theory breaks down when
the Ricci scalar vanishes (and the radius of transition is sent to infinity),
in a way similar to what has been found to occur around sources on a Minkowski
background.
| [
{
"created": "Wed, 22 Dec 2004 18:29:16 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2005 16:37:56 GMT",
"version": "v2"
}
] | 2009-10-07 | [
[
"Deffayet",
"Cedric",
""
]
] | We investigate the cosmological perturbations of the brane-induced (Dvali-Gabadadze-Porrati) model which exhibits a van Dam-Veltman-Zakharov (vDVZ) discontinuity when linearized over a Minkowski background. We show that the linear brane scalar cosmological perturbations over an arbitrary Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time have a well defined limit when the radius of transition between 4D and 5D gravity is sent to infinity with respect to the background Hubble radius. This radius of transition plays for the brane-induced gravity model a role equivalent to the Compton wavelength of the graviton in a Pauli-Fierz theory, as far as the vDVZ discontinuity is concerned. This well defined limit is shown to obey the linearized 4D Einstein's equations whenever the Hubble factor is non vanishing. This shows the disappearance of the vDVZ discontinuity for general FLRW background, and extends the previously know result for maximally-symmetric space-times of non vanishing curvature. Our reasoning is valid for matter with simple equation of state such as a scalar field, or a perfect fluid with adiabatic perturbations, and involves to distinguish between space-times with a vanishing scalar curvature and space-times with a non vanishing one. We also discuss the validity of the linear perturbation theory, in particular for those FLRW space-times where the Ricci scalar is vanishing only on a set of zero measure. In those cases, we argue that the linear perturbation theory breaks down when the Ricci scalar vanishes (and the radius of transition is sent to infinity), in a way similar to what has been found to occur around sources on a Minkowski background. |
0906.2919 | Piotr Bizon | Piotr Bizon, Tadeusz Chmaj, Andrzej Rostworowski, Stanislaw Zajac | Late-time tails of wave maps coupled to gravity | 7 pages, 3 figures | Class.Quant.Grav.26:225015,2009 | 10.1088/0264-9381/26/22/225015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the late-time asymptotic behavior for solutions of Einstein's
equations with the wave map matter. Solutions starting from small compactly
supported $\ell$-equivariant initial data with $\ell\geq 1$ are shown to decay
as $t^{-(2\ell+2)}$ at future timelike infinity and as $u^{-(\ell+1)}$ at
future null infinity.
| [
{
"created": "Tue, 16 Jun 2009 13:01:56 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Bizon",
"Piotr",
""
],
[
"Chmaj",
"Tadeusz",
""
],
[
"Rostworowski",
"Andrzej",
""
],
[
"Zajac",
"Stanislaw",
""
]
] | We consider the late-time asymptotic behavior for solutions of Einstein's equations with the wave map matter. Solutions starting from small compactly supported $\ell$-equivariant initial data with $\ell\geq 1$ are shown to decay as $t^{-(2\ell+2)}$ at future timelike infinity and as $u^{-(\ell+1)}$ at future null infinity. |
2403.09373 | Tatsuya Daniel | Tatsuya Daniel, Leah Jenks | Gravitational Waves in Chern-Simons-Gauss-Bonnet Gravity | 15 pages, 1 figure | Phys. Rev. D 109 (2024) 12, 124012 | 10.1103/PhysRevD.109.124012 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the four-dimensional effective field theory arising from
heterotic string theory is general relativity with both a Chern-Simons and
Gauss-Bonnet term. We study the propagation of gravitational waves in this
combination of Chern-Simons and Gauss-Bonnet gravity, both of which have an
associated scalar field, the axion and the dilaton respectively, that are
kinetically coupled. We review how the combination of dynamical Chern-Simons
and Gauss-Bonnet gravities can arise from string theory as corrections to
general relativity and show how the gravitational wave waveform is modified in
such a theory. We compare our results to a novel framework recently introduced
for parametrizing the parity-violating sector (Chern-Simons), and use that to
guide our construction of a similar parametrization for the parity-conserving
(Gauss-Bonnet) sector. In general, we find that the contributions from the
parity-violating and parity-conserving sectors are similar. Moreover, the
kinetic coupling between the axion and dilaton introduces an extra contribution
to the parity-violating sector of the gravitational waves. Using our
parametrization, we are able to comment on initial constraints for the theory
parameters, including the time variations of the axion and dilaton.
| [
{
"created": "Thu, 14 Mar 2024 13:20:35 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Daniel",
"Tatsuya",
""
],
[
"Jenks",
"Leah",
""
]
] | It is known that the four-dimensional effective field theory arising from heterotic string theory is general relativity with both a Chern-Simons and Gauss-Bonnet term. We study the propagation of gravitational waves in this combination of Chern-Simons and Gauss-Bonnet gravity, both of which have an associated scalar field, the axion and the dilaton respectively, that are kinetically coupled. We review how the combination of dynamical Chern-Simons and Gauss-Bonnet gravities can arise from string theory as corrections to general relativity and show how the gravitational wave waveform is modified in such a theory. We compare our results to a novel framework recently introduced for parametrizing the parity-violating sector (Chern-Simons), and use that to guide our construction of a similar parametrization for the parity-conserving (Gauss-Bonnet) sector. In general, we find that the contributions from the parity-violating and parity-conserving sectors are similar. Moreover, the kinetic coupling between the axion and dilaton introduces an extra contribution to the parity-violating sector of the gravitational waves. Using our parametrization, we are able to comment on initial constraints for the theory parameters, including the time variations of the axion and dilaton. |
0706.4431 | Luca Parisi | Luca Parisi, Marco Bruni, Roy Maartens, Kevin Vandersloot | The Einstein static universe in Loop Quantum Cosmology | 12 pages, 7 figures; v2: minor changes to match published version in
Classical and Quantum Gravity | Class.Quant.Grav.24:6243-6254,2007 | 10.1088/0264-9381/24/24/007 | null | gr-qc astro-ph hep-th | null | Loop Quantum Cosmology strongly modifies the high-energy dynamics of
Friedman-Robertson-Walker models and removes the big-bang singularity. We
investigate how LQC corrections affect the stability properties of the Einstein
static universe. In General Relativity, the Einstein static model with positive
cosmological constant Lambda is unstable to homogeneous perturbations. We show
that LQC modifications can lead to a centre of stability for a large enough
positive value of Lambda.
| [
{
"created": "Fri, 29 Jun 2007 14:32:47 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jan 2008 14:00:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Parisi",
"Luca",
""
],
[
"Bruni",
"Marco",
""
],
[
"Maartens",
"Roy",
""
],
[
"Vandersloot",
"Kevin",
""
]
] | Loop Quantum Cosmology strongly modifies the high-energy dynamics of Friedman-Robertson-Walker models and removes the big-bang singularity. We investigate how LQC corrections affect the stability properties of the Einstein static universe. In General Relativity, the Einstein static model with positive cosmological constant Lambda is unstable to homogeneous perturbations. We show that LQC modifications can lead to a centre of stability for a large enough positive value of Lambda. |
1309.1918 | N Khusnutdinov | Nail Khusnutdinov | Bremstrahlung in wormhole spacetime with infinitely short throat | 11p, 3 figures | Phys. Rev. D89, 024012 (2014) | 10.1103/PhysRevD.89.024012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the total energy loss and spectral density of uniformly moving
electrically charged particles in the spacetime of a wormhole with an
infinitely short throat. We show that the total energy loss $\mathcal{E} \sim
e^2v\gamma a^2/b^3$, where $\gamma$ is relativistic factor, $a$ is the radius
of the wormhole's throat and $b$ is the impact factor. The spectrum of the
energy for particles radially moving through the wormhole's throat $\mathcal{E}
\sim e^2v\gamma/a$. The spectral density of the total energy has a maximum at
frequency $\omega_m \sim v\gamma/b$ and at $\omega_m \sim v\gamma /a$ for
radial motion.
| [
{
"created": "Sat, 7 Sep 2013 23:36:23 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jan 2014 22:23:57 GMT",
"version": "v2"
}
] | 2014-01-17 | [
[
"Khusnutdinov",
"Nail",
""
]
] | We consider the total energy loss and spectral density of uniformly moving electrically charged particles in the spacetime of a wormhole with an infinitely short throat. We show that the total energy loss $\mathcal{E} \sim e^2v\gamma a^2/b^3$, where $\gamma$ is relativistic factor, $a$ is the radius of the wormhole's throat and $b$ is the impact factor. The spectrum of the energy for particles radially moving through the wormhole's throat $\mathcal{E} \sim e^2v\gamma/a$. The spectral density of the total energy has a maximum at frequency $\omega_m \sim v\gamma/b$ and at $\omega_m \sim v\gamma /a$ for radial motion. |
1802.00492 | Ott Vilson | Laur J\"arv, Mihkel R\"unkla, Margus Saal and Ott Vilson | Nonmetricity formulation of general relativity and its scalar-tensor
extension | 7 pages, 2 figures, REVTeX, clarifications and references added,
version accepted for publication in PRD | Phys. Rev. D 97, 124025 (2018) | 10.1103/PhysRevD.97.124025 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein's celebrated theory of gravitation can be presented in three forms:
general relativity, teleparallel gravity, and the rarely considered before
symmetric teleparallel gravity. Extending the latter, we introduce a new class
of theories where a scalar field is coupled nonminimally to nonmetricity $Q$,
which here encodes the gravitational effects like curvature $R$ in general
relativity or torsion $T$ in teleparallel gravity. We point out the
similarities and differences with analogous scalar-curvature and scalar-torsion
theories by discussing the field equations, role of connection, conformal
transformations, relation to $f(Q)$ theory, and cosmology. The equations for
spatially flat universe coincide with those of teleparallel dark energy, thus
allowing to explain accelerating expansion.
| [
{
"created": "Thu, 1 Feb 2018 21:26:57 GMT",
"version": "v1"
},
{
"created": "Thu, 10 May 2018 20:10:59 GMT",
"version": "v2"
}
] | 2018-06-12 | [
[
"Järv",
"Laur",
""
],
[
"Rünkla",
"Mihkel",
""
],
[
"Saal",
"Margus",
""
],
[
"Vilson",
"Ott",
""
]
] | Einstein's celebrated theory of gravitation can be presented in three forms: general relativity, teleparallel gravity, and the rarely considered before symmetric teleparallel gravity. Extending the latter, we introduce a new class of theories where a scalar field is coupled nonminimally to nonmetricity $Q$, which here encodes the gravitational effects like curvature $R$ in general relativity or torsion $T$ in teleparallel gravity. We point out the similarities and differences with analogous scalar-curvature and scalar-torsion theories by discussing the field equations, role of connection, conformal transformations, relation to $f(Q)$ theory, and cosmology. The equations for spatially flat universe coincide with those of teleparallel dark energy, thus allowing to explain accelerating expansion. |
1607.08466 | Louis Witten | Louis Witten | On a New Formulation of Vacuum Axisymmetric Solutions of general
Relativity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Axisymmetric Solutions of the vacuum Einstein equations are found in the
Papapetrou-Weyl gauge. The solutions depend on two pairs of functionals, each
pair of two functions depends on a different arbitrarily chosen function of one
variable. Some examples are given.
| [
{
"created": "Thu, 28 Jul 2016 14:14:21 GMT",
"version": "v1"
}
] | 2016-07-29 | [
[
"Witten",
"Louis",
""
]
] | Axisymmetric Solutions of the vacuum Einstein equations are found in the Papapetrou-Weyl gauge. The solutions depend on two pairs of functionals, each pair of two functions depends on a different arbitrarily chosen function of one variable. Some examples are given. |
2201.01957 | Salvatore Capozziello | H. Abedi, S. Capozziello, M. Capriolo, and A. M. Abbassi | Gravitational energy-momentum pseudo-tensor in Palatini and metric
$f(R)$ gravity | 9 pages | null | 10.1016/j.aop.2022.168796 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the gravitational energy-momentum pseudo-tensor
$\tau^\mu_{\phantom{\mu}\nu}$ in both Palatini and metric approaches to $f(R)$
gravity. We then obtain the related cosmological gravitational energy density.
Considering a flat Friedmann-Lema\^itre-Robertson-Walker spacetime, the energy
density complex of matter and gravitation vanishes in the metric approach, but
results non-vanishing in the Palatini formalism. This feature could be relevant
in order to physically discriminate between the two approaches.
| [
{
"created": "Thu, 6 Jan 2022 07:49:57 GMT",
"version": "v1"
}
] | 2022-03-02 | [
[
"Abedi",
"H.",
""
],
[
"Capozziello",
"S.",
""
],
[
"Capriolo",
"M.",
""
],
[
"Abbassi",
"A. M.",
""
]
] | We derive the gravitational energy-momentum pseudo-tensor $\tau^\mu_{\phantom{\mu}\nu}$ in both Palatini and metric approaches to $f(R)$ gravity. We then obtain the related cosmological gravitational energy density. Considering a flat Friedmann-Lema\^itre-Robertson-Walker spacetime, the energy density complex of matter and gravitation vanishes in the metric approach, but results non-vanishing in the Palatini formalism. This feature could be relevant in order to physically discriminate between the two approaches. |
1207.4891 | Matthew J. Lake Dr | Matthew Lake and Jun'ichi Yokoyama | Cosmic strings with twisted magnetic flux lines and wound-strings in
extra dimensions | 34 pages, no figures. Revised text incorporating the results included
in erratum JCAP 08 (2013) E01 | JCAP 09 (2012) 030 [JCAP 08 (2013) E01] | 10.1088/1475-7516/2012/09/030 | RESCEU-37/12 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a generalization of the Nielsen-Olesen ansatz, in an
abelian-Higgs model with externally coupled charge, which describes strings
with twisted magnetic flux lines in the vortex core. The solution does not
possess cylindrical symmetry, which leads to the existence of components of
conserved momentum, both around the core-axis and along the length of the
string. In addition, we consider a model of F-strings with rotating, geodesic
windings in the compact space of the Klebanov-Strassler geometry and determine
matching conditions which ensure energy and momentum conservation when loops
chop off from the long-string network. We find that the expressions for the
constants of motion, which determine the macroscopic string dynamics, can be
made to coincide with those for the twisted flux line string, suggesting that
extra-dimensional effects for F-strings may be mimicked by field- theoretic
structure in topological defects.
| [
{
"created": "Fri, 20 Jul 2012 09:37:45 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2012 12:08:38 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Oct 2012 07:39:03 GMT",
"version": "v3"
},
{
"created": "Wed, 17 Jul 2013 08:24:44 GMT",
"version": "v4"
},
{
"cre... | 2015-09-30 | [
[
"Lake",
"Matthew",
""
],
[
"Yokoyama",
"Jun'ichi",
""
]
] | We consider a generalization of the Nielsen-Olesen ansatz, in an abelian-Higgs model with externally coupled charge, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra-dimensional effects for F-strings may be mimicked by field- theoretic structure in topological defects. |
2405.06035 | David Hilditch | David Hilditch | Solving the Einstein Equations Numerically | 36 pages, 2 figures. Invited chapter for the edited book "New
Frontiers in GRMHD Simulations" (Eds. C. Bambi, Y. Mizuno, S. Shashank and F.
Yuan, Springer Singapore, expected in 2024) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are many complementary approaches to the construction of solutions to
the field equations of general relativity. Among these, numerical approximation
offers the only possibility to compute a variety of dynamical spacetimes, and
so has come to play an important role for theory and experiment alike.
Presently we give a brief introduction to this, the science of numerical
relativity. We discuss the freedom in formulating general relativity as an
initial (boundary) value problem. We touch on the fundamental concepts of
well-posedness and gauge freedom and review the standard computational methods
employed in the field. We discuss the physical interpretation of numerical
spacetime data and end with an overview of a number of 3d codes that are either
in use or under active development.
| [
{
"created": "Thu, 9 May 2024 18:10:02 GMT",
"version": "v1"
}
] | 2024-05-13 | [
[
"Hilditch",
"David",
""
]
] | There are many complementary approaches to the construction of solutions to the field equations of general relativity. Among these, numerical approximation offers the only possibility to compute a variety of dynamical spacetimes, and so has come to play an important role for theory and experiment alike. Presently we give a brief introduction to this, the science of numerical relativity. We discuss the freedom in formulating general relativity as an initial (boundary) value problem. We touch on the fundamental concepts of well-posedness and gauge freedom and review the standard computational methods employed in the field. We discuss the physical interpretation of numerical spacetime data and end with an overview of a number of 3d codes that are either in use or under active development. |
1207.1177 | Kourosh Nozari | Kourosh Nozari and Sara Islamzadeh | Tunneling of massive and charged particles from noncommutative
Reissner-Nordstr\"{o}m black hole | 10 pages, 2 figures | Astrophys. Space Sci. 347 (2013) 299 | 10.1007/s10509-013-1532-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive charged and uncharged particles tunneling from commutative
Reissner-Nordstrom black hole horizon has been studied with details in
literature. Here, by adopting the coherent state picture of spacetime
noncommutativity, we study tunneling of massive and charged particles from a
noncommutative inspired Reissner-Nordstrom black hole horizon. We show that
Hawking radiation in this case is not purely thermal and there are correlations
between emitted modes. These correlations may provide a solution to the
information loss problem. We also study thermodynamics of noncommutative
horizon in this setup.
| [
{
"created": "Thu, 5 Jul 2012 07:36:20 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Nozari",
"Kourosh",
""
],
[
"Islamzadeh",
"Sara",
""
]
] | Massive charged and uncharged particles tunneling from commutative Reissner-Nordstrom black hole horizon has been studied with details in literature. Here, by adopting the coherent state picture of spacetime noncommutativity, we study tunneling of massive and charged particles from a noncommutative inspired Reissner-Nordstrom black hole horizon. We show that Hawking radiation in this case is not purely thermal and there are correlations between emitted modes. These correlations may provide a solution to the information loss problem. We also study thermodynamics of noncommutative horizon in this setup. |
1005.2904 | Debraj Roy | Rabin Banerjee, Debraj Roy, Saurav Samanta | Lagrangian generators of the Poincare gauge symmetries | Latex2e, 15 pages, 1 figure; (v2) Appendix containing discussion on
applications of Lagrangian generators added | Phys.Rev.D82:044012,2010 | 10.1103/PhysRevD.82.044012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have systematically computed the generators of the symmetries arising in
Poincare gauge theory formulation of gravity, both in 2+1 and 3+1 dimensions.
This was done using a completely Lagrangian approach. The results are expected
to be valid in any dimensions, as seen through lifting the results of the 2+1
dimensional example into the 3+1 dimensional one.
| [
{
"created": "Mon, 17 May 2010 12:31:31 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Aug 2010 17:03:24 GMT",
"version": "v2"
}
] | 2010-08-10 | [
[
"Banerjee",
"Rabin",
""
],
[
"Roy",
"Debraj",
""
],
[
"Samanta",
"Saurav",
""
]
] | We have systematically computed the generators of the symmetries arising in Poincare gauge theory formulation of gravity, both in 2+1 and 3+1 dimensions. This was done using a completely Lagrangian approach. The results are expected to be valid in any dimensions, as seen through lifting the results of the 2+1 dimensional example into the 3+1 dimensional one. |
gr-qc/0002022 | Ulf Nilsson | U. S. Nilsson and C. Uggla | General Relativistic Stars : Polytropic Equations of State | 31 pages, 10 figures | Annals Phys. 286 (2001) 292-319 | 10.1006/aphy.2000.6090 | null | gr-qc | null | In this paper, the gravitational field equations for static spherically
symmetric perfect fluid models with a polytropic equation of state,
$p=k\rho^{1+1/n}$, are recast into two complementary 3-dimensional {\it
regular} systems of ordinary differential equations on compact state spaces.
The systems are analyzed numerically and qualitatively, using the theory of
dynamical systems. Certain key solutions are shown to form building blocks
which, to a large extent, determine the remaining solution structure. In one
formulation, there exists a monotone function that forces the general
relativistic solutions towards a part of the boundary of the state space that
corresponds to the low pressure limit. The solutions on this boundary describe
Newtonian models and thus the relationship to the Newtonian solution space is
clearly displayed. It is numerically demonstrated that general relativistic
models have finite radii when the polytropic index $n$ satisfies $0\leq n
\lesssim 3.339$ and infinite radii when $n\geq 5$. When $3.339\lesssim n<5$,
there exists a 1-parameter set of models with finite radii and a finite number,
depending on $n$, with infinite radii.
| [
{
"created": "Fri, 4 Feb 2000 12:32:46 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nilsson",
"U. S.",
""
],
[
"Uggla",
"C.",
""
]
] | In this paper, the gravitational field equations for static spherically symmetric perfect fluid models with a polytropic equation of state, $p=k\rho^{1+1/n}$, are recast into two complementary 3-dimensional {\it regular} systems of ordinary differential equations on compact state spaces. The systems are analyzed numerically and qualitatively, using the theory of dynamical systems. Certain key solutions are shown to form building blocks which, to a large extent, determine the remaining solution structure. In one formulation, there exists a monotone function that forces the general relativistic solutions towards a part of the boundary of the state space that corresponds to the low pressure limit. The solutions on this boundary describe Newtonian models and thus the relationship to the Newtonian solution space is clearly displayed. It is numerically demonstrated that general relativistic models have finite radii when the polytropic index $n$ satisfies $0\leq n \lesssim 3.339$ and infinite radii when $n\geq 5$. When $3.339\lesssim n<5$, there exists a 1-parameter set of models with finite radii and a finite number, depending on $n$, with infinite radii. |
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