String Theory Seminar
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Mon, 10/10/2011 12:00 |
Arthur Lipstein (Oxford) |
String Theory Seminar  |
L3 |
| The study of superconformal Chern-Simons theories has led to a deeper understanding of M-theory and a new example of the AdS/CFT correspondence. In this talk, I will give an overview of superconformal Chern-Simons theories and their gravity duals. I will also describe some recent work on scattering amplitudes in these theories. | |||
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Mon, 17/10/2011 12:00 |
David Andriot (LMU Munich) |
String Theory Seminar |
L3 |
| Four-dimensional (4d) supergravities with non-geometric terms in their potential are very promising models for phenomenology. Indeed, these terms, generated by so-called non-geometric fluxes, generically help to obtain de Sitter vacua, or to stabilise moduli. Unfortunately, deriving these theories from a compactified ten-dimensional (10d) supergravity has not been achieved so far. One reason is that non-geometric fluxes do not seem to match any 10d field, and another reason is the appearance of global issues in 10d non-geometric configurations. After reviewing some background material, we present in this talk a solution to the two previous issues. Thanks to a field redefinition, we make the non-geometric Q-flux appear in a 10d action, which only differs from the NSNS action by a total derivative. In addition, this new action is globally well-defined, at least in some examples, and one can then perform the dimensional reduction to recover the 4d non-geometric potential. We also mention an application to the heterotic string. Based on 1106.4015. | |||
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Mon, 24/10/2011 12:00 |
Michael Klaput (Oxford) |
String Theory Seminar |
L3 |
| String compactifications incorporating non-vanishing H-flux have received increased attention over the past decade for their potential relevance to the moduli stabilization problem. Their internal spaces are in general not Kähler and, therefore, not Calabi-Yau. In the heterotic string an important technical problem is to construct gauge bundles on such spaces. I will present a method of how to explicitly construct gauge bundles over homogeneous nearly-Kähler manifolds of dimension six and discuss some of the arising implications for model building. | |||
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Mon, 31/10/2011 12:00 |
Nikolay Gromov (King's College London) |
String Theory Seminar |
L3 |
| We compute three-point functions of single trace operators in planar N = 4 SYM. We consider the limit where one of the operators is much smaller than the other two. We find a precise match between weak and strong coupling in the Frolov-Tseytlin classical limit for a very general class of classical solutions. To achieve this match we clarify the issue of back-reaction and identify precisely which three-point functions are captured by a classical computation. | |||
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Mon, 07/11/2011 12:00 |
Davide Cassani (King's College London) |
String Theory Seminar |
L3 |
| Consistent truncations have proved to be powerful tools in the construction of new string theory solutions. Recently, they have been employed in the holographic description of condensed matter systems. In the talk, I will present a rich class of supersymmetric consistent truncations of higher-dimensional supergravity which are based on geometric structures, focusing on the tri-Sasakian case. Then I will discuss some applications, including a general result relating AdS backgrounds to solutions with non-relativistic Lifshitz symmetry. | |||
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Mon, 14/11/2011 12:00 |
Lukas Witkowski (Oxford) |
String Theory Seminar |
L3 |
| I will study the sequestering of blow-up fields through a CFT in a toroidal orbifold setting. In particular, I will examine the disk correlator between orbifold blow-up moduli and matter Yukawa couplings. Blow-up moduli appear as twist fields on the worldsheet which introduce a monodromy condition for the coordinate field X. Thus I will focus on how the presence of twist field affects the CFT calculation of disk correlators. Further, I will explain how the results are relevant to suppressing soft terms to scales parametrically below the gravitino mass. Last, I want to explore the relevance of our calculation for the case of smooth Calabi-Yaus. | |||
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Mon, 21/11/2011 12:00 |
James Sparks (Oxford) |
String Theory Seminar |
L3 |
| In just the last year it has been realized that one can define supersymmetric gauge theories on non-trivial compact curved manifolds, coupled to a background R-symmetry gauge field, and moreover that expectation values of certain BPS operators reduce to finite matrix integrals via a form of localization. I will argue that a general approach to this topic is provided by the gauge/gravity correspondence. In particular, I will present several examples of supersymmetric gauge theories on different 1-parameter deformations of the three-sphere, which have a large N limit, together with their gravity duals (which are solutions to Einstein-Maxwell theory). The Euclidean gravitational partition function precisely matches a large N matrix model evaluation of the field theory partition function, as an exact function of the deformation parameter. | |||
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Mon, 28/11/2011 12:00 |
Joan Simon (University of Edinburgh) |
String Theory Seminar |
L3 |
I will discuss the dynamical emergence of IR conformal invariance describing the low energy excitations of near-extremal R-charged global AdS black holes. To keep some non-trivial dynamics in the sector of  SYM captured by the near horizon limits describing these IR physics, we are lead to study large N limits in the UV theory involving near vanishing horizon black holes. I will consider both near-BPS and non-BPS regimes, emphasising the differences in the local AdS throats emerging in both cases. I will compare these results with the predictions obtained by Kerr/CFT, obtaining a natural quantisation for the central charge of the near-BPS emergent IR CFT describing the open strings stretched between giant gravitons. |
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