String Theory Seminar
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Mon, 19/01/2009 12:00 |
Maximo Bañados (Pontificia Universidad Católica de Chile and Oxford) |
String Theory Seminar  |
L3 |
| In an attempt to define the ground state of general relativity as a state with no metric we arrive at a bigravity action. This action has surprising applications to cosmology and is competitive with the standard dark matter paradigm. Fluctuations and CMB spectra are briefly discussed. | |||
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Mon, 26/01/2009 12:00 |
Andrei Starinets (Oxford) |
String Theory Seminar |
L3 |
| Gauge-string duality relates transport properties of certain strongly interacting quantum field theories at finite temperature/density to spectra of normal modes of black branes in dual supergravity backgrounds. The duality serves as a source of quantitative information about the physics of strongly coupled relativistic plasmas as well as a source of qualitative insights into the properties of nuclear matter created in heavy ion collision experiments. It may also help to understand non-equilibrium behavior of black holes/branes. We reflect on recent progress in this field. | |||
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Mon, 02/02/2009 12:00 |
Maxime Gabella (Oxford) |
String Theory Seminar |
L3 |
| We use generalized complex geometry to study the AdS/CFT correspondence in type IIB string theory. | |||
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Mon, 09/02/2009 12:00 |
Jarah Evslin (Trieste) |
String Theory Seminar |
L3 |
| We define an action of ordinary and Narain T-duality on an arbitrary torus bundle by applying Buscher and Narain's formulations patchwise. In general it changes the topology of the compactification manifold and its NS 3-form flux, for example in the case of a circle bundle it interchanges the Chern class with a pushforward of the flux. It nonetheless provides a candidate duality of the full string theory because it preserves several topological and geometric invariants such as the twisted K-theory in type II and the tadpole and supersymmetry conditions in non-Kahler heterotic compactifications. | |||
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Mon, 16/02/2009 12:00 |
Andre Lukas (Oxford) |
String Theory Seminar |
L3 |
| We present a straightforward, algebraic method for calculating the Yukawa couplings of a large class of non-standard embedding heterotic compactifications on Calabi-Yau threefolds. Our methodology covers, although is not restricted to, the positive monads over complete intersection Calabi-Yau manifolds. The algorithm involves the manipulation of polynomials and can be straightforwardly implemented on a computer. We present explicit examples and show how models with one Higgs multiplet and a rank-one mass matrix can be engineered. | |||
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Mon, 23/02/2009 12:00 |
Dario Martelli (Swansea) |
String Theory Seminar |
L3 |
| I discuss different approaches for developing a holographic correspondence for theories with non-relativistic conformal symmetry. In particular, I will describe certain gravity backgrounds with non-relativistic conformal symmetry and their embedding in string theory. One method uses supergravity solution generating techniques. Another method is based on certain novel consistent Kaluza-Klein truncations with massive modes. These truncations have also other applications, in the context of the AdS/CFT correspondence, or otherwise. | |||
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Mon, 02/03/2009 12:00 |
Volker Braun (Dublin Institute of Advanced Studies) |
String Theory Seminar |
L3 |
| Conjecturally, there are only finitely many possible fundamental groups of Calabi-Yau manifolds. I will start by reviewing some of the known examples of such "Calabi-Yau groups" and their importance or string theory. Then I will present some progress towards the classification of the free quotients of complete intersection Calabi-Yau manifolds in products of projective spaces. | |||
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Mon, 09/03/2009 12:00 |
Paul Howe (King's College London) |
String Theory Seminar |
L3 |
| Recent developments in computational techniques have shown that UV divergences can be tested at higher loop orders than is possible using standard Feynman diagrams. The results of these calculations are summarised. It is argued that they do not, as yet, contradict expectations from symmetry arguments. The latter lead to the expectation that D=4, N=8 supergravity is likely to diverge at five loops unless hitherto unknown mechanisms are at work. In the technical part of the talk the role of algebraic renormalisation and cohomological methods is highlighted. | |||
