Relativity Seminar
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Tue, 13/10/2009 12:00 |
Prof E T Newman (University of Pittsburgh) |
Relativity Seminar  |
L3 |
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Tue, 20/10/2009 12:00 |
Alan Rendall (AEI Golm) |
Relativity Seminar |
L3 |
| Two classes of solutions of the Einstein equations with symmetry which are frequently studied are the Bianchi and Gowdy models. The aim of this talk is to explain certain relations between these two classes of spacetimes which can provide insights into the dynamics of both. In particular it is explained that the special case of the Gowdy models known as circular loop spacetimes are Bianchi models in disguise. Generalizations of Gowdy spacetimes which can be thought of as inhomogeneous perturbations of some of the Bianchi models are introduced. Results concerning their dynamics are presented. | |||
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Tue, 03/11/2009 12:00 |
Piotr Bizon (Jagiellonian University) |
Relativity Seminar |
L3 |
| I will present recent joint work with Tadek Chmaj and Andrzej Rostworowski concerning late-time behavior of self-gravitating massless fields. We show that the asymptotic convergence to a static equilibrium (Minkowski or Schwarzschild) is an essentially nonlinear phenomenon which cannot, despite many assertions to the contrary in the literature, be properly described by the theory of linearized perturbations on a fixed static asymptotically flat background (so called Price's tails). To substantiate this claim in the case of small initial data we compute the late-time tails (both the decay rate and the amplitude) in four and higher even spacetime dimensions using nonlinear perturbation theory and we verify the results numerically. The reason for considering this problem in higher dimensions was motivated by the desire to demonstrate an accidental and misleading character of equality of decay rates of linear and nonlinear tails in four dimensions. | |||
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Tue, 17/11/2009 12:00 |
Harvey Reall (DAMTP Cambridge) |
Relativity Seminar |
L3 |
| Algebraic classification of the Weyl tensor is an important tool for solving the Einstein equation. I shall review the classification for spacetimes of dimension greater than four, and recent progress in using it to construct new exact solutions. The higher-dimensional generalization of the Goldberg-Sachs theorem will be discussed. | |||
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Tue, 01/12/2009 12:00 |
James Lucietti (Imperial) |
Relativity Seminar |
L3 |
| Extremal black holes are of interest as they are expected have simpler quantum descriptions than their non-extremal counterparts. Any extremal black hole solution admits a well defined notion of a near horizon geometry which solves the same field equations. I will describe recent progress on the general understanding of such near horizon geometries in four and higher dimensions. This will include the proof of near-horizon symmetry enhancement and the explicit classification of near-horizon geometries (in a variety of settings). I will also discuss how one can use such results to prove classification/uniqueness theorems for asymptotically flat extremal vacuum black holes in four and five dimensions. | |||
