Found at least 20 result(s)
Regular Seminar JeongHyuck Park (Sogang University)
at: 15:30 room 410  abstract: String theory predicts its own gravity rather than GR. In General Relativity the metric is the only geometric and gravitational field, whereas in string theory the closedstring massless sector comprises a skewsymmetric Bfield and the string dilaton in addition to the metric. Furthermore, these three fields transform into each other under Tduality. This hints at a natural augmentation of GR: upon treating the whole closed string massless sector as stringy graviton fields, Double Field Theory may evolve into `Stringy Gravity'. Equipped with an O(D,D) covariant differential geometry beyond Riemann, we spell out the definitions of the stringy Einstein curvature tensor and the stringy EnergyMomentum tensor. Equating them, all the equations of motion of the closed string massless sector are unified into a single expression which we dub the Einstein Double Field Equations. 
Regular Seminar AmirKian KashaniPoor (ENS)
at: 15:00 room B103  abstract: The topological string is a simplified version of physical string theory. It is of interest because it computes the BPS spectrum of relevant string theory compactifications, but also because it shares structural properties of physical string theory, Dualities and symmetries which often must be argued for arduously in the physical string can often be verified by computation in the topological setting. The central observable of the theory is the topological string partition function Z_top. This quantity has an eerie habit of making surprise appearances in many areas of mathematical physics. Numerous techniques exist for its computation in various expansions in parameters of the theory, yet to date, no satisfactory closed form for this quantity is known. In this talk, after reviewing notions of topological string theory with an emphasis on the interplay between worldsheet and target space physics (one of the structural similarities between the physical and the topological string alluded to above), I will report on progress in computing Z_top in settings where it is related to enigmatic 6d theories. 
Regular Seminar Alejandro CaboBizet (KCL)
at: 13:15 room K4.31  abstract: I will start by sketching the computation of the topologically twisted index on H2xS1 and its evaluation in ABJM theory in the large N limit with k=1. Then after, I will review the key points behind the construction of magnetically charged (hyperbolic) AdS4 black holes on STU gauged SUGRA and will conclude by stating how the aformentioned index  upon extremization  coincides with the entropy of the latter black holes in the large N limit (with k=1). 
Regular Seminar ChongSun Chu (NCTS, Hsinchu and Taiwan, Natl. Tsing Hua U.)
at: 11:30 room 610  abstract: In this talk, I will discuss about the holography of boundary Conformal Field theory. I will show how boundary Weyl Anomaly can be obtained from holography. New universal relations between the shape dependence of Casimir effects and boundary Weyl anomaly will also be pointed out and discussed from the point of view of holography. 
Regular Seminar Jose Miguel FigueroaO'Farrill (Edinburgh)
at: 13:15 room G01 Norfolk Building  abstract: I will report on joint work with Andrea Santi outlining an algebraic reformulation of the classification problem of elevendimensional supergravity backgrounds. The basic object of study is the Killing superalgebra of the background, whose algebraic structure has recently been elucidated. If time permits I will also comment on work also involving Paul de Medeiros applying these techniques to the construction of rigidly supersymmetric theories in curved spaces. 
Exceptional Seminar   ()
at: 10:00 room tba  abstract: 29 August  3 September, King's College London.
Registration will be closed on 8 July 2016 or when positions are filled. 
Exceptional Seminar RakKyeong Seong (KIAS)
at: 15:30 room K6.63  abstract: In this talk, I will discuss Type IIA brane configurations consisting of D4branes suspended between NS5branes which represent a large class of 2d (0,2) quiver gauge theories. We call these new constructions Brane Brick models. These are Tdual to D1branes over singular toric CalabiYau 4folds and encode information about the probed CalabiYau geometry as well as the corresponding GLSM. If time permits, I will present how Brane Brick models naturally realise in terms of a brane configuration 2d (0,2) GaddeGukovPutrov triality. 
Regular Seminar YangHui He (City)
at: 15:00 room B103  abstract: We establish a precise correspondence between the ABC Conjecture and N=4 superYangMills theory. This is achieved by combining three ingredients: (i) Elkies' method of mapping ABCtriples to elliptic curves in his demonstration that ABC implies Mordell/Faltings; (ii) an explicit pair of elliptic curve and associated Belyi map given by KhadjaviScharaschkin; and (iii) the fact that the bipartite branetiling/dimer model for a gauge theory with toric moduli space is a particular dessin d'enfant in the sense of Grothendieck. We explore this correspondence for the highest quality ABCtriples as well as large samples of random triples. The Conjecture itself is mapped to a statement about the fundamental domain of the toroidal compactification of the string realization of N=4 SYM. 
Regular Seminar YangHui He (City)
at: 14:00 room G.O. Jones 610  abstract: We study the web of correspondences linking the exceptional Lie algebras E8,7,6 and the sporadic simple groups Monster, Baby and the largest Fischer group. We will survey some old observations from the perspective of Moonshine and representation theory and present some new ones from that of congruence groups and enumerative geometry. Based on joint work with John McKay. 
Regular Seminar Diego RodriguezGomez (Universidad de Oviedo)
at: 14:00 room G.O. Jones 610  abstract: 5d theories can be at fixed points, in many cases exhibiting rather amusing properties. In this talk we will study several properties of these fixed point theories. In particular, we will describe how to put them supersymmetrically in curved spaces. As a consequence, we will discuss when a deformation to a YangMills theory is possible. The latter typically exhibit a smaller global symmetry that that of the fixed point theory, which, from the YM point of view, appears as an enhanced symmetry. In this enhancement instantons play a pivotal role, and we will discuss several aspects of these. 
Triangular Seminar Diego RodriguezGomez (University of Oviedo)
at: 15:00 room GO Jones 610  abstract: Counting operators in supersymmetric field theories is very interesting, as the corresponding generating functions encode properties of the field theory. In this lecture we will mostly concentrate on 4d SUSY field theories. After reviewing some basic notions about SUSY field theories leading to the notion of chiral ring, we will introduce a generating function enumerating operators in the ring. This function is the socalled Hilbert series. In the case of SCFTs with a gravity dual, we will show how this function recovers geometric properties of the dual gravity background. The uses of the Hilbert series go beyond this, since, as we will see, being a counting of operators, it is of relevance in the computation of instanton partition functions for pure gauge theories. In the second part of the lecture we will briefly touch upon these issues. 
Regular Seminar Jose FernandezMelgarejo (Harvard)
at: 13:30 room H503  abstract: We study the general formulation of gauged supergravity in seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry. 
Regular Seminar Simon CaronHuot (NBI)
at: 14:00 room G.O. Jones 610  abstract: Physical systems with unexpected, or `hidden,’ symmetries have often played an important role in physics, beginning with the classical Kepler problem whose LaplaceRungeLenz vector ensures the closure of planetary orbits, and degeneracies of the Hydrogen spectrum. I will describe how precisely the same symmetry governs a unique fourdimensional quantum field theory, a maximally supersymmetric (`N=4') cousin of the stronginteraction YangMills theory. After reviewing progress in recent years in using these symmetries to solve this model, I will describe novel applications involving massive particles. Combining the LaplaceRungeLenz vector with relativity then yields a novel way to calculate the spectrum of its Hydrogenlike bound states, including relativistic corrections. Based on 1408.0296. 
Regular Seminar YangHui He (City University)
at: 13:15 room G.01  abstract: Inspired by the multiplicative nature of the Ramanujan modular discriminant, Delta, we consider physical realizations of certain multiplicative products over the Dedekind etafunction in two parallel directions: the generating function of BPS states in certain heterotic orbifolds and elliptic K3 surfaces associated to congruence subgroups of the modular group. We show that they are, after string duality to type II, the same K3 surfaces admitting Nikulin automorphisms. In due course, we will present some identities arising from qexpansions as well as relations to the sporadic Mathieu group M24. 
Triangular Seminar YangHui He (City University)
at: 15:30 room Francis Bancroft 1.15  abstract:

Regular Seminar Ron ReidEdwards (Hull)
at: 14:00 room H503  abstract: Abelian gerbes play a ubiquitous role in string and supergravity theories. It is conjectured that nonabelian gerbe theories exist, but a satisfactory explicit construction of such a theory has not yet been achieved. Inspired by the possibility that a nonabelian theory of gerbes may be possible on nonconventional spacetimes, I will consider a toy model on a lattice that allows one to make some progress in this problem. In this talk, I will show how abelian gerbe theories may be described naturally on the lattice. I will outline a nonabelian generalisation and show how, under dimensional reduction, such theories give rise to lattice YangMills. 
Regular Seminar Diego RodriguezGomez (Oviedo U.)
at: 14:00 room G.O. Jones 208  abstract: In this talk I will review recent progress in understanding aspects of 5d gauge theories. Under certain circumstances these can be at fixed points admitting a large N limit, whose gravity dual we will discuss. Such gravity dual suggests a yet more general class of quivertype fixed point theories which can sometimes be understood in terms of Sduality. To this matter the braneweb construction of the theories will prove very helpful, yielding new insights which we will test using the 5d superconformal index. 