Forthcoming Seminars › Seminar Series

String Theory Seminar

Mon, 16/01/2012
12:00 		Nadav Drukker (King's College London) String Theory Seminar Add to calendar L3
Generalized quark-antiquark potential of N=4 SYM at weak and strong coupling
I will present a two-parameter family of Wilson loop operators in N = 4 supersymmetric Yang-Mills theory which interpolates smoothly between the 1/2 BPS line or circle and a pair of antiparallel lines. These observables capture a natural generalization of the quark-antiquark potential. These loops are calculated on the gauge theory side to second order in perturbation theory and in a semiclassical expansion in string theory to one-loop order. The resulting determinants are given in integral form and can be evaluated numerically for general values of the parameters or analytically in a systematic expansion around the 1/2 BPS configuration. I will comment about the feasibility of deriving all-loop results for these Wilson loops.
Mon, 23/01/2012
12:00 		Andrea Prinsloo (University of Cape Town) String Theory Seminar Add to calendar L3
Giant Gravitons in the ABJM Duality
I shall describe the construction of the four-brane giant graviton on $ \mathrm{AdS}_4\times \mathbb{CP}^3 $ (extended and moving in the complex projective space), which is dual to a subdeterminant operator in the ABJM model. This dynamically stable, BPS configuration factorizes at maximum size into two topologically stable four-branes (each wrapped on a different $ \mathbb{CP}^2 \subset \mathbb{CP}^3 $ cycle) dual to ABJM dibaryons. Our study of the spectrum of small fluctuations around this four-brane giant provides good evidence for a dependence in the spectrum on the size, $ \alpha_0 $, which is a direct result of the changing shape of the giant’s worldvolume as it grows in size. I shall finally comment upon the implications for operators in the non-BPS, holomorphic sector of the ABJM model.
Mon, 30/01/2012
12:00 		Jihye Seo (McGill University) String Theory Seminar Add to calendar L3
Singularity structure and massless dyons of pure N = 2, d = 4 theories with SU(r+1) and Sp(2r) gauge groups
We study pure Seiberg-Witten theories with $ SU(r+1) $ and $ Sp(2r) $ gauge groups with no flavors. We study singularity loci of moduli space of the Seiberg-Witten curve. Using exterior derivative and discriminant operators, we can find Argyres-Douglas loci of the SW theory. We also compute BPS charges of the massless dyons of $ SU $ and $ Sp $ SW theory. In a detailed example of $ C_2=Sp(4) $, we find 6 points in the moduli space where we have 2 massless BPS dyons, and 3 of them give Argyres-Douglas loci. We show that BPS charges of the massless dyons jump as we go across Argyres-Douglas loci, giving an explicit example of Argyres-Douglas loci living inside the wall of marginal stability. (Based on work in progress with Keshav Dasgupta)
Mon, 06/02/2012
12:00 		Rhys Davies (Oxford) String Theory Seminar Add to calendar L3
The MSSM spectrum from the heterotic standard embedding
I will describe the recent construction of new supersymmetric compactifications of the heterotic string which yield just the spectrum of the MSSM at low energies. The starting point is the standard embedding solution on a Calabi-Yau manifold with Euler number -6 with various choices of Wilson lines, i.e., various choices of discrete holonomy for the gauge bundle. Although they yield three net generations of standard model matter, such models necessarily have a larger gauge group than the standard model, as well as exotic matter content. Families of stable bundles can be obtained by deformation of these simple solutions, the deformation playing the dual role of partially breaking the gauge group and reducing the matter content, and in this way we construct more realistic models. The moduli space breaks up into various branches depending on the initial choice of Wilson lines, and on eight of these branches we find models with exactly the standard model gauge group, three generations of quarks and leptons, two Higgs doublets, and no other massless charged states. I will also comment on why these are possibly the unique models of this type.
Mon, 13/02/2012
12:00 		Sanjaye Ramgoolam (Queen Mary University of London) String Theory Seminar Add to calendar L3
Quantum states to brane geometries via fuzzy moduli space
The moduli space of supersymmetric (eighth-BPS) giant gravitons in $ AdS_5 \times S^5 $ is a limit of projective spaces. Quantizing this moduli space produces a Fock space of oscillator states, with a cutoff $ N $ related to the rank of the dual $ U(N) $ gauge group. Fuzzy geometry provides the ideal set of techniques for associating points or regions of moduli space to specific oscillator states. It leads to predictions for the spectrum of BPS excitations of specific worldvolume geometries. It also leads to a group theoretic basis for these states, containing Young diagram labels for $ U(N) $ as well as the global $ U(3) $ symmetry group. The problem of constructing gauge theory operators corresponding to the oscillator states and  some recent progress in this direction are explained.
Mon, 20/02/2012
12:00 		Hadi Godazgar (University of Cambridge) String Theory Seminar Add to calendar L3
M-theory dualities and generalised geometry
In this talk we will review M-theory dualities and recent attempts to make these dualities manifest in eleven-dimensional supergravity. We will review the work of Berman and Perry and then outline a prescription, called non-linear realisation, for making larger duality symmetries manifest. Finally, we will explain how the local symmetries are described by generalised geometry, which leads to a duality-covariant constraint that allows one to reduce from generalised space to physical space.
Mon, 27/02/2012
12:00 		Aristomenis Donos (Imperial College London) String Theory Seminar Add to calendar L3
Holographic stripes and helical superconductors
The AdS/CFT correspondence is a powerful tool to analyse strongly coupled quantum field theories. Over the past few years there has been a surge of activity aimed at finding possible applications to condensed matter systems. One focus has been to holographically realise various kinds of phases via the construction of fascinating new classes of black hole solutions. In this framework, I will discuss the possibility of describing finite temperature phase transitions leading to spontaneous breaking of translational invariance of the dual field theory at strong coupling. Along with the general setup I will also discuss specific string/M theory embeddings of the corresponding symmetry breaking modes leading to the description of such phases.
Mon, 05/03/2012
12:00 		Cyril Closset (Weizmann Institute) String Theory Seminar Add to calendar L3
Three-sphere partition function, counterterms and supergravity
The partition function of 3d N=2 superconformal theories on the 3-sphere can be computed exactly by localization methods. I will explain some sublteties associated to that important result. As a by-product, this analysis establishes the so-called F-maximization principle for N=2 SCFTs in 3d: the exact superconformal R-charge maximizes the 3-sphere free energy F=-log Z.

For any corrections/updates to these listings, please contact seminars [-at-] maths [dot] ox [dot] ac [dot] uk.

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