| 51. |
- Evangelista, Gianpaolo
(författare)
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The Present Status of the VIRGO Central Interferometer
- 2002
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 19:7, s. 1421-1428
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Tidskriftsartikel (refereegranskat)abstract
- The VIRGO Central Interferometer (CITF) is a short suspended interferometer operated with the central area elements of the VIRGO detector. The main motivation behind the CITF is to allow the integration and debugging of a large part of the subsystems of VIRGO while the construction of the long arms of the antenna is being completed. This will permit a faster commissioning of the full-size antenna. In fact, almost all the main components of the CITF, with the exception of the large mirrors and a few other details, are the same as those to be used for the full-size detector. In this paper the present status of the VIRGO CITF is reported.
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| 52. |
- Fjällborg, Mikael, 1970
(författare)
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Static cylindrically symmetric spacetimes
- 2007
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 24:9, s. 2253-2269
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Tidskriftsartikel (refereegranskat)abstract
- We prove the existence of static solutions to the cylindrically symmetric Einstein-Vlasov system, and we show that the matter cylinder has finite extension in two of the three spatial dimensions. The same results are also proved for a quite general class of equations of state for perfect fluids coupled to the Einstein equations, extending the class of equations of state considered by Bicak et al (2004 Class. Quantum Grav. 21 1583). We also obtain this result for the Vlasov-Poisson system.
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| 53. |
- Garcia-Parrado, Alfonso, 2000-
(författare)
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Dynamical laws of superenergy in General Relativity
- 2008
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 25, s. 015006-015032
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Tidskriftsartikel (refereegranskat)abstract
- The Bel and Bel-Robinson tensors were introduced nearly 50 years ago in an attempt to generalize to gravitation the energy-momentum tensor of electromagnetism. This generalization was successful from the mathematical point of view because these tensors share mathematical properties which are remarkably similar to those of the energy-momentum tensor of electromagnetism. However, the physical role of these tensors in general relativity has remained obscure and no interpretation has achieved wide acceptance. In principle, they cannot represent energy and the term superenergy has been coined for the hypothetical physical magnitude lying behind them. In this work, we try to shed light on the true physical meaning of superenergy by following the same procedure which enables us to give an interpretation of the electromagnetic energy. This procedure consists in performing an orthogonal splitting of the Bel and Bel-Robinson tensors and analyzing the different parts resulting from the splitting. In the electromagnetic case such splitting gives rise to the electromagnetic energy density, the Poynting vector and the electromagnetic stress tensor, each of them having a precise physical interpretation which is deduced from the dynamical laws of electromagnetism (Poynting theorem). The full orthogonal splitting of the Bel and Bel-Robinson tensors is more complex but, as expected, similarities with electromagnetism are present. Also the covariant divergence of the Bel tensor is analogous to the covariant divergence of the electromagnetic energy-momentum tensor and the orthogonal splitting of the former is found. The ensuing equations are to the superenergy what the Poynting theorem is to electromagnetism. Some consequences of these dynamical laws of superenergy are explored, among them the possibility of defining superenergy radiative states for the gravitational field.
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| 54. |
- Goliath, Martin, et al.
(författare)
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Spatially self-similar spherically symmetric perfect-fluid models
- 1998
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 15:1, s. 167-186
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Tidskriftsartikel (refereegranskat)abstract
- Einstein's field equations for spatially self-similar spherically symmetric perfect-fluid models are investigated. The field equations are rewritten as a first-order system of autonomous differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system is reduced as far as possible and so that the reduced phase space becomes compact and regular. The system is subsequently analysed qualitatively with the theory of dynamical systems
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| 55. |
- Goliath, Martin, et al.
(författare)
-
Timelike self-similar spherically symmetric perfect-fluid models
- 1998
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 15:9, s. 2841-2863
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Tidskriftsartikel (refereegranskat)abstract
- Einstein's field equations for timelike self-similar spherically symmetric perfect-fluid models are investigated. The field equations are rewritten as a first-order system of autonomous differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system is reduced as far as possible and so that the reduced phase space becomes compact and regular. The system is subsequently analysed qualitatively using the theory of dynamical systems
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| 56. |
- Gomez-Lobo, A.G.-P., et al.
(författare)
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Kerr initial data
- 2008
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 25:20
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Tidskriftsartikel (refereegranskat)abstract
- Exploiting a (3+1) analysis of the Mars-Simon tensor, conditions on a vacuum initial data set ensuring that its development is isometric to a subset of the Kerr spacetime are found. These conditions are expressed in terms of the vanishing of a positive scalar function defined on the initial data hypersurface. Applications of this result are discussed. © 2008 IOP Publishing Ltd.
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| 57. |
- Gran, Ulf, 1973, et al.
(författare)
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AdS backgrounds from black hole horizons
- 2013
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 30:5, s. Art. no. 055014-
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Tidskriftsartikel (refereegranskat)abstract
- We utilize the classification of IIB horizons with 5-form flux to present a unified description for the geometry of AdS(n), n = 3, 5, 7 solutions. In particular, we show that all such backgrounds can be constructed from eight-dimensional 2-strong Calabi-Yau geometries with torsion which admit some additional isometries. We explore the geometry of AdS(3) and AdS(5) solutions but we do not find AdS(7) solutions.
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| 58. |
- Gran, Ulf, 1973, et al.
(författare)
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Dynamical symmetry enhancement near massive IIA horizons
- 2015
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 32:23, s. Art. Nr. 235004-
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Tidskriftsartikel (refereegranskat)abstract
- We prove that Killing horizons in massive IIA supergravity preserve an even number of supersymmetries, and that their symmetry algebra contains an ??(2,R) subalgebra, confirming the conjecture of [5]. We also prove a new class of Lichnerowicz type theorems for connections of the spin bundle whose holonomy is contained in a general linear group.
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| 59. |
- Greitz, J., et al.
(författare)
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The tensor hierarchy simplified
- 2014
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 31:8
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Tidskriftsartikel (refereegranskat)abstract
- A compact formulation of the field-strengths, Bianchi identities and gauge transformations for tensor hierarchies in gauged maximal supergravity theories is given. A key role in the construction is played by the recently-introduced tensor hierarchy algebra.
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| 60. |
- Guica, Monica, et al.
(författare)
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Behind the geon horizon
- 2015
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 32:5
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Tidskriftsartikel (refereegranskat)abstract
- We explore the Papadodimas-Raju prescription for reconstructing the region behind the horizon of one-sided black holes in AdS/CFT in the case of the. P2 geon-a simple, analytic example of a single-sided, asymptotically AdS(3) black hole, which corresponds to a pure CFT state that thermalizes at late times. We show that in this specific example, the mirror operators involved in the reconstruction of the interior have a particularly simple form: the mirror of a single trace operator at late times is just the corresponding single trace operator at early times. We use some explicit examples to explore how changes in the state modify the geometry inside the horizon.
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