Place: Potter Room (first floor, Pavilion B of the CMS)
Time: Thursdays, 1pm
Organiser: Dr Hadi Godazgar, Dr Joao Gomes
Michaelmas 2014
09Oct2014: Exotic Branes and 3D Supergravity
Daniel Mayerson (University of Amsterdam) [Transparencies]
Abstract: String theory has been known for quite a while to contain nonperturbative objects called Dbranes in addition to the fundamental strings the theory is named after. However, fairly recently, new types of membranes in string theory are being studied with increasing interest: the socalled "exotic branes" (also known by other names). These exotic branes have the interesting feature that their spacetime is multivalued or nongeometric; this means that when you travel in a circle around the brane, the resulting spacetime looks different from that which you started out with! It is of considerable interest to study and classify the possible types of such exotic branes that can exist in string theory. To study them, we can work in a 3D theory (of maximal supergravity), where the exotic branes are just point particles. In this theory, we can at least classify the supersymmetric point particles, thereby gaining insight into what kind of supersymmetric exotic branes exist in string theory. This problem reduces to that of classifying nilpotent orbits associated with the Uduality group (E_8), for which various mathematical results are known. It can be shown that the only allowed supersymmetric configurations are 1/2, 1/4, 1/8, and 1/16 BPS, and their respective nilpotent orbits can be given explicitly. On the other hand, it turns out exceedingly difficult to translate this classification into a simple criterion for supersymmetry in terms of the nonAbelian (monodromy) charges of the objects.
16Oct2014: Integrable deformations of AdS3 x S3 x M4 strings
Ben Hoare (HumboldtUniversity of Berlin) [Transparencies]
Abstract: In this talk we will explore integrable deformations of the GxG/G_0 supercoset sigma model that plays a role in the GreenSchwarz formulation of superstrings on AdS3 x S3 x T4 (G = PSU(1,12)) and AdS3 x S3 x S3 x S1 (G = D(2,1;?)). After reviewing the single parameter deformation of Delduc, Magro and Vicedo, which treats the two copies of G symmetrically, the main focus of the talk will be the construction of an asymmetric twoparameter deformation based on ?lim?ík's biYangBaxter sigma model. Some evidence will also be presented for the existence of a threeparameter deformation. Various interesting limits (including the squashed threesphere, the Pohlmeyerreduced theory and the mirror model) of the corresponding deformed metrics will be analyzed and the issue of whether these models describe deformations of superstrings will be briefly discussed.
23Oct2014: TBA
Henning Samtleben (ENS Lyon) [Transparencies]
30Oct2014: TBA
Nima Doroud (DAMTPCambridge) [Transparencies]
06Nov2014: TBA
HengYu Chen (National Taiwan University) [Transparencies]
13Nov2014: TBA
James Lucietti (University of Edinburgh) [Transparencies]
20Nov2014: TBA
Ted Erler (LMUMunich) [Transparencies]
27Nov2014: TBA
Michael Ferlaino (Swansea University) [Transparencies]
04Dec2014: TBA
Glenn Barnich (ULB Brussels) [Transparencies]
Easter 2014
24Apr2014:Brane deformations in supergravity
Vasilis Niarchos (University of Crete) [Transparencies]
Abstract:I will present recent work on the physics of longwavelength supersymmetric deformations of brane solutions in supergravity. We will see how familiar concepts from Dbrane theory, like the DiracBornInfeld action and the kappasymmetry condition, arise directly from the supergravity equations and will discuss their implications on the SUGRA /DBI correspondence. As a concrete example, we will consider the case of M5 branes in elevendimensional supergravity.
01May2014: Resurgent Analysis in Quantum Theories: Perturbative Theory and Beyond
Ines Aniceto (Lisbon, IST Maths) [Transparencies]
Abstract:In order to study the weakly coupled regime of some given quantum theory we often make use of perturbative expansions of the physical quantities of interest. But such expansions are often divergent, with zero radius of convergence, and defined only as asymptotic series. In fact, this divergence is connected to the existence of nonperturbative contributions, i.e. instanton effects that cannot be simply captured by a perturbative analysis. The theory of resurgence is a mathematical tool which allows us to effectively study this connection and its consequences. Moreover, it allows us to construct a full nonperturbative solution from perturbative data. In this talk, I will review the essential role of resurgence theory in the description of the analytic solution behind the asymptotic series. I will then relate resurgence to the socalled Stokes phenomena and phase transitions using a simple example, and will further discuss some major applications of this construction.
08May2014: The superconformal index of the (2,0) theory with defects
Mathew Bullimore (Perimeter) [Transparencies]
Abstract:String theory predicts the existence of a class of interacting superconformal field theories in six dimensions which arise on the worldvolume of coincident M5 branes. There are important defect operators in these theories corresponding to intersecting M2 and M5 branes. I will explain how to compute the superconformal index in the presence of such defects using fivedimensional supersymmetric gauge theory and show that they are in onetoone correspondence with the characters of irreducible representations of a class of chiral algebras.
15May2014: Conformal Partial Waves, the building blocks of the Conformal Bootstrap
Hugh Osborn (DAMTP) [Transparencies]
Abstract:
22May2014: Hyperkahler Sigma Model and Field Theory on GibbonsHawking Spaces
Anindya Dey (U Texas) [Transparencies]
Abstract:We will introduce a deformed version of the 3d hyperkahler sigma model which arises from the compactification of d=4,N=2 gauge theories on a GibbonsHawking space. After discussing extensions of the relevant hyperkahler identities from the standard story, we will derive the condition for which the deformed sigma model preserves 4 out of the 8 supercharges. Using supersymmetry considerations, we will also demonstrate that the contribution of the NUT center to the sigma model path integral is a holomorphic section of a certain holomorphic line bundle over the hyperkahler target. As a concrete example, we will discuss the case where the original 4d theory is a U(1) super YangMills and show that the NUT center contribution in this case is the Jacobi theta function.
29May2014:TBA
Guido Festuccia (NBI) [Transparencies]
Abstract:
05Jun2014: TBA
Paul Heslop (Durham University) [Transparencies]
Abstract:
12Jun2014: TBA
Diego Hofman (UVA) [Transparencies]
Abstract:
19Jun2014: TBA
TBC [Transparencies]
Abstract:
Past Seminars
 2014:
Lent 23Jan2014: Colorkinematics duality in YangMills theory from string amplitudes
Oliver Schlotterer (AEI)) [Transparencies]
Abstract: I will review the duality between color and kinematics in gauge theories?a striking resemblance between the color and polarization or momenta dependent parts of Yang Mills (YM) amplitudes. As a key benefit, it severely facilitates the construction of gravity amplitudes from gauge theory. However, manifestation of the duality requires a very particular arrangement of quartic vertices among cubic diagrams which could not yet be systematized within the field theory setup. In this talk, I will provide examples at tree level (based on 1104.5224) and at oneloop (work in progress) how the field theory limit of superstring amplitudes naturally leads to dualitysatisfying representations of YM amplitudes.  30Jan2014: KacMoody Fourier modes and BPS instantons in string theory
Axel Kleinschmidt (AEI) [Transparencies]
Abstract:Uduality of type II string theory in less than three spacetime dimensions is conjecturally associated with the infinitedimensional KacMoody structures E9, E10 and E11 . The implementation of these Uduality groups for string theory observables requires the study of automorphic forms on KacMoody groups and results of this study will be presented, highlighting the link to BPS instantons.  13Feb2014: Dimensional reductions of D=11 supergravity and generalised geometry
Hadi Godazgar (DAMTP) [Transparencies]
Abstract:In this talk I will review recent progress on understanding reductions of D=11 supergravity to fourdimensional maximal gauged supergravities using generalised geometry. Questions regarding consistency of reductions, uplift ans\?atze and what theories can be obtained in four dimensions by reducing D=11 supergravity are seen to be tractable within the framework of a generalised geometric reformulation of D=11 supergravity.  20Feb2014: Superstring amplitudes with pure spinor cohomology methods
Carlos Mafra (DAMTP) [Transparencies]
Abstract: In this talk I will show how superstring amplitudes in ten dimensions assume simple forms when written as objects in the cohomology of pure spinor superspace. This realization motivates a systematic study of the cohomology using the vertex operator algebra in the pure spinor formalism as a tool to antecipate results for higherpoint amplitudes at a given loop order. I will also show how these studies led to a multiparticle generalization of the standard tendimensional SYM equations of motion.  27Feb2014: Black hole thermodynamics revisited
Alejandra Castro (University of Amsterdam) [Transparencies]
Abstract:The analytic structure of a black hole encodes important information about its thermodynamics. In this talk I'll describe the relation between monodromy data and the thermodynamic properties of the conjectured description of black hole microstates by a 2D CFT. I'll discuss the extend of this evidence (both in favor and against the conjecture).  06Mar2014: On entanglement in higher spin theories
Eric Perlmutter (DAMTP) [Transparencies]
Abstract:There has been phenomenal recent progress in computing CFT entanglement and Renyi entropies, holographically and otherwise. We extend these investigations to the higher spin regime  where sensible notions of geometry are sorely lacking  by computing ground state Renyi entropy in certain classes of holographic CFTs with higher spin symmetry. Our calculations are performed at both classical and oneloop level, from gravity and CFT. Along the way, we establish perturbative methods for computing Renyi entropy in any CFT, with or without higher spin symmetry and in various spacetime dimensions.  13Mar2014: BPS Quivers and N=2 superconformal theories
Simone Giacomelli (ULB) [Transparencies]
Abstract:The BPS spectrum of a large class of N=2 theories can be encoded in an oriented graph called BPS quiver. In this talk I will review the BPS quiver technique and the 4d/2d correspondence introduced by Cecotti, Neitzke and Vafa. In the second part of the talk, based on a work in collaboration with Sergio Cecotti and Michele Del Zotto, I will explain how the BPS quiver technology can be used to study a new class of N=2 superconformal models construceted via Type IIB geometric engineering. The computation of various quantities of interest such as scaling dimensions of chiral operators and central charges can be related via the 4d/2d correspondence to twodimensional problems.  20Mar2014: Holographic Quantum Quench and Critical Points
Sumit Das (University of Kentucky) [Transparencies]
Abstract:Holographic methods are used to study the problem of quantum quench across critical points. These have led to new insight into the origin of KibbleZurek scaling for?slow? quench and to new universal scaling laws for ?fast? quench. This talk will describe some recent work in this area.

Easter 24Apr2014:Brane deformations in supergravity
Vasilis Niarchos (University of Crete) [Transparencies]
Abstract:I will present recent work on the physics of longwavelength supersymmetric deformations of brane solutions in supergravity. We will see how familiar concepts from Dbrane theory, like the DiracBornInfeld action and the kappasymmetry condition, arise directly from the supergravity equations and will discuss their implications on the SUGRA /DBI correspondence. As a concrete example, we will consider the case of M5 branes in elevendimensional supergravity.

 23Jan2014: Colorkinematics duality in YangMills theory from string amplitudes
 2013:
Lent 17Jan2013: Holomorphic blocks in 3 dimensions
Sara Pasquetti (Surrey) [Transparencies]
Abstract: We show that sphere partition functions and indices of 3 dimensional, N = 2, gauge theories can be decomposed into a sum of products of a universal set of holomorphic blocks. The blocks count BPS states of a theory on R2 x S1 and are in onetoone correspondence with the theory's massive vacua. The blocks turn out to have a wealth of surprising properties such as a Stokes phenomenon and have interesting dual interpretations in analytically continued ChernSimons theory and open topological strings.  24Jan2013: On the physical meaning and consequences of the loop IR divergences in global dS
Emil Akhmedov (ITEP) [Transparencies]
Abstract: The tak is based on arXiv:1209.4448, arXiv:1202.1202 and arXiv:1110.2257. We show that in global de Sitter space its isometry is broken by the loop IR divergences for any invariant vacuum state of the massive scalars. We derive kinetic equation in global de Sitter space. It follows from the DysonSchwinger equation of the SchwingerKeldysh diagrammatic technique in IR limit and allows to understand the physical meaning and consequences of the loop IR divergences. In many respects the isometry breaking in global dS is similar to the one in the contracting Poincare patch of de Sitter space. Hence, as a warm up exercise we study the kinetic equation and properties of its solutions in the expanding and contracting Poincare patches of de Sitter space. Quite unexpectedly we find that under some initial conditions there is an explosive production of massive particles in the expanding Poincare patch.  31Jan2013: Dynamical simulations of holographic matrix models
Curtis Asplund (Leuven) [Transparencies]
Abstract: The holographic AdS/CFT duality of string theory lets you study quantum black holes indirectly via their dual field theory states. Most existing studies have focused on equilibrium or static quantities, such as entropies, temperatures, etc., or nearequilibrium quantities such as thermal Green's functions, linear transport coefficients and quasinormal modes. We wanted to learn about the real time, nonequilibrium dynamics of the field theory states and so made numerical simulations of some holographic matrix models [including flat space (BFSS) and plane wave (BMN) versions]. More precisely, these are simulations of the classical dynamics of the bosonic sectors of these models, which should be appropriate for high temperatures. This is in the same spirit as a molecular dynamics simulation of a fluid. I'll present the current results from our ongoing analysis of these simulations, in which we observe thermalization, fluctuations and other behavior. I'll then discuss and invite your comments on the relations to supergravity black holes and other future work. The talk is based on the papers arXiv:1104.5469 and arXiv:1211.3425.  07Feb2013: Supersymmetric Field Theories on ThreeManifolds and Applications
Cyril Closset (Weizmann Institute) [Transparencies]
Abstract: In the first part of my talk, I will present a general classification of Riemannian threemanifolds on which one can put 3d N=2 supersymmetric field theories while preserving some amount of supersymmetry. This formalism clarifies the relationship between the extra couplings necessary to preserve supersymmetry in curved space, on the one hand, and various operators of the flat space theory, on the other hand. In the second part of the talk I will present some simple applications of this formalism. In particular I will present exact results for various twopoint functions of N=2 SCFTs which were hitherto out of reach.  12Feb2013: Higher spin symmetry and its breaking in CFTs
Alexander Zhiboedov (Princeton) [Transparencies]
Abstract: I will review the use of higher spin symmetry in conformal field theories (CFTs). First, I will demonstrate that the theory is essentially free when the higher spin symmetry is present. Then I will discuss different ways of breaking the higher spin symmetry. This will lead to the idea of 3d bosonization and prediction of certain critical exponents in the 3d Ising model.  14Feb2013: Polylogarithms in treelevel open string calculations
Johannes Broedel (Zurich ETH) [Transparencies]
Abstract: Recent investigations have revealed a beautiful structure in open string treelevel amplitudes: they can be organized in terms of classes of multiple zeta values, which in turn provide the link to a related Hopfalgebra structure. While the open string treelevel function can be written in an extraordinarily simple form, the actual calculation was subject to difficulties and thus confined to low multiplicities and low orders in the inverse string tension. In this talk I will describe how to employ polylogarithms in order to algebraically obtain results for any multiplicity efficiently. Those results can be used to test the underlying algebra for previously unaccessible scenarios.  28Feb2013: Landau Levels and Holography
Mike Blake (DAMTP) [Transparencies]
Abstract: One of the outstanding problems facing applied holography is the development of a complete understanding of how the traditional Fermi surfaces of condensed matter physics are realized in the bulk. Whilst the general problem is very hard, in this talk I shall describe a regime in which progress can be made. In the presence of a strong magnetic field the dynamics of fermions undergoes a dimensional reduction and we are able to use Coleman's classic technique of bosonization. This allows us to obtain a description of the Landau level physics of the boundary theory in terms of a `star' of gravitating sineGordon kinks in the bulk.  5Mar2013: New transport properties of holographic superfluids
Daniel Fernandez (University of Barcelona) [Transparencies]
Abstract: In the context of holography applied to condensed matter theory, I will present an analysis of transport properties of pwave superfluids by means of a gravity dual. Fluctuation modes in the SU(2) EinsteinYangMills theory are considered, and phenomenological implications are derived. Due to the spatial anisotropy of the system, a nonuniversal shear viscosity is obtained, along with a new coefficient associated to normal stress differences. I will also discuss how the transport phenomena in this model is related to the thermoelectric, flexoelectric and piezoelectric effects (mixing of electric current, heat flux and mechanical stress).  07Mar2013: Harmonic Rmatrices for Scattering Amplitudes and Spectral Regularization
Jan Plefka (Humboldt) [Transparencies]
Abstract: Planar N=4 super YangMills appears to be integrable. While this allows to find this theory's exact spectrum, integrability has hitherto been of no direct use for scattering amplitudes. To remedy this, we deform all scattering amplitudes by a spectral parameter. The deformed treelevel fourpoint function turns out to be essentially the oneloop Rmatrix of the integrable N=4 spin chain satisfying the YangBaxter equation. Deformed onshell threepoint functions yield novel threeleg Rmatrices satisfying bootstrap equations. Finally, we supply initial evidence that the spectral parameter might find its use as a novel symmetryrespecting regulator replacing dimensional regularization. Its physical meaning is a local deformation of particle helicity, a fact which might be useful for a much larger class of nonintegrable fourdimensional field theories.  14Mar2013: Holography without translational symmetry
David Vegh (CERN) [Transparencies]
Abstract: We propose massive gravity as a holographic framework for describing a class of strongly interacting quantum field theories with broken translational symmetry. At finite chemical potential, the gravity duals are charged black holes in asymptotically antide Sitter spacetime. The conductivity in these systems generally exhibits a Drude peak that approaches a delta function in the massless gravity limit, while the optical conductivity shows an emergent scaling law.

Easter 11Apr2013: Landau levels and incompressible states in dense holographic matter.
Gordon Semenoff (British Columbia) [Transparencies]
Abstract: .  25Apr2013: String theory amplitudes and UV behavior of half maximal supergravity.
Piotr Tourkine (CEA Saclay) [Transparencies]
Abstract: In this talk I shall discuss various ways in which string theory may be used to constrain the ultraviolet (UV) behavior of its low energy limits; supergravity theories. I shall begin by reviewing the links between string theory amplitudes and the UV behavior of theories of supergravity. It appears that some aspects of those links can be well described in the mathematical framework of "tropical geometry", a recent mathematical theory that I shall quickly discuss. The most important part of the talk is then dedicated to the vanishing of the threeloop UV divergence in fourgraviton amplitudes in four dimensionnal halfmaximal supergravity (with matter fields). We shall see how a nonrenormalisation theorem in Heterotic string rules out this divergence and postpones it to the fourloop order.  2May2013: Unification of Type IIA and IIB Supergravities.
JeongHyuck Park (DAMTP/Sogang University, Seoul) [Transparencies]
Abstract: This talk aims to explain our recent construction of D=10 type II supersymmetric double field theory with 32 supersymmetries, to the full order in fermions. The constructed action unifies type IIA and IIB supergravities in a manifestly covariant manner with respect to O(10,10) Tduality and a pair of local Lorentz groups, or Spin(1,9) \times Spin(9,1), besides the usual general covariance of supergravities. While the theory is unique, the solutions are twofold. Type IIA and IIB supergravities are identified as two different types of solutions rather than two different theories. References: arXiv:1210.5078 (N=2) arXiv:1206.3478 (bosonic N=2) arXiv:1112.0069 (N=1).  14May2013: Dynamical Twisting and the pure spinor formalism.
Nathan Berkovits (Univ. Estadual Paulista) [Transparencies]
Abstract: .  16May2013: On the nonlinear deformations of highspin gauge symmetries.
Massimo Taronna (Max Planck) [Transparencies]
Abstract: In this talk we address the classification of consistent cubic interactions involving symmetric highspin fields in any constant curvature background, together with the corresponding nonlinearly deformed gauge symmetries.  23May2013: An infalling observer and the black hole information paradox in AdS/CFT.
Kyriakos Papadodimas (University of Groningen) [Transparencies]
Abstract: I will describe how the interior of a black hole can be reconstructed from the point of view of the dual gauge theory in the framework of the AdS/CFT correspondence. I will argue that the infalling observer does not notice anything special when crossing the horizon and that it is possible to resolve the information paradox without dramatic violations of effective field theory, in contrast to predictions by the recent fuzzball and firewall proposals.  30May2013: Quantum Black Holes, Localization, and Mock Modular Forms.
Atish Dabholkar (Jussieu) [Transparencies]
Abstract: There has been considerable progress recently in computing finite size quantum corrections to the BekensteinHawkingWald entropy for a class of black holes in string theory. These computations of `exact' quantum entropy of black holes involve a new application of localization techniques in a gravitational context and reveal surprising connections with the fascinating mathematics of mock modular forms. In the broader context of holography and the AdS/CFT correspondence, such finite size quantum gravity corrections correspond to finite N corrections in the gauge theory. I will outline why such corrections are interesting, how to compute them, and what we can learn from them.  6Jun2013: Some aspects of high energy scattering and integrability.
Romuald Janik (Jagellonian University) [Transparencies]
Abstract: In this talk I will consider high energy scattering in the Regge limit. After reviewing the current status both at weak and at strong coupling, I will proceed to describe the difficulties associated with an integrable description and give a construction of a classical string solution which reproduces the classical part of the strong coupling BFKL intercept. I will also comment on the algebraic curve description and complementary work at weak coupling.  11Jun2013: Minimal Model Holography.
Matthias Gaberdiel (ETH Zurich) [Transparencies]
Abstract: The conjectured relation between higher spin theories on AdS spaces and weakly coupled conformal field theories is reviewed. I shall then explain the evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall describe recent progress towards relating these higher spin theories to string theory.  13Jun2013: Superselection Sectors in AdS/CFT.
Aron Wall (UC Santa Barbara) [Transparencies]
Abstract: AdS/CFT is a duality relating the degrees of freedom in a D dimensional bulk gravity theory to a (D1) dimensional theory living on the boundary. I will argue that in fact the boundary theory contains only a subset of the bulk observables. For each state of the boundary theory, there are multiple bulk states dual to it, which can be operationally distinguished by observers who fall across event horizons. Based on arXiv:1210.3590.  02Jul2013: 3d quivers gauge theories and integrability.
Peter Koroteev (Perimeter) [Transparencies]
Abstract: I will discuss 3d quiver gauge theories of A_N type and their moduli space of supersymmetric vacua. According to NekrasovShatatshvili the moduli space of vacua can be parameterized by solutions of Bethe equations of an anisotropic 1d spin chain. We shall relate various dualities in gauge theory with those of the spin chains as well as a very interesting connection of quantum spin chains with Hitchin systems.

Michaelmas 3Oct2013: Resurgence at work in the principal chiral model
Aleksey Cherman (FTPI) [Transparencies]
Abstract: I will discuss the physical role of nonperturbative saddle points of path integrals in theories without instantons, using the example of the asymptotically free twodimensional principal chiral model (PCM). Standard topological arguments based on homotopy considerations suggest no role for nonperturbative saddles in such theories. However, resurgence theory, which unifies perturbative and nonperturbative physics, predicts the existence of several types of nonperturbative saddles associated with features of the largeorder structure of perturbation theory. These points are illustrated in the PCM , where we found new nonperturbative `fracton? saddle point field configurations, and give a quantum interpretation of previously discovered `uniton? unstable classical solutions. The fractons lead to a semiclassical realization of IR renormalons in the circlecompactified theory, and yield the microscopic mechanism of the mass gap of the PCM .  10Oct2013: From conformal to Einstein gravity on twistor space
Tim Adamo (DAMTP) [Transparencies]
Abstract: There have been numerous recent results in our understanding of scattering amplitudes in gauge theory and gravity, many of which have been influenced by something called twistor theory. This talk will explore how we can study general relativity using twistor action functionals by exploiting the embedding of Einstein gravity inside conformal gravity (a conformally invariant theory with 4thorder equations of motion). This has implications for the study of ?scattering amplitudes? in (anti)de Sitter space, the existence of a MHV formalism for gravity, and several other (hopefully) exciting arenas.  17Oct2013: 3D Bosonization and ChernSimons Vector Models
Guy GurAri (Weizmann Institute) [Transparencies]
Abstract: ChernSimons theories coupled to vector matter exhibit interesting phenomena. In the planar limit, these theories are conjectured to be holographically dual to generalized theories of gravity, involving highspin fields. This is a weakweak holographic duality that is in some aspects very simple, and may serve as a toy model for deepening our understanding of both holography and string theory. On the CFT side, exact calculations performed in the planar limit, along with constraints imposed by a ?slightlybroken? highspin symmetry, have led to many exact results. These have uncovered the details of a 3D bosonization duality, relating theories with bosonic matter to theories with fermionic matter. I will present dynamical evidence for this duality.  24Oct2013: Collisions in AdS and the thermalisation of heavyion collisions
Wilke van der Schee (Utrecht University) [Transparencies]
Abstract: Numerically simulating colliding planar gravitational shock waves in AdS gives rise to rich and interesting dynamics. Wide shocks come to a full stop and expand hydrodynamically, as was previously found by Chesler and Yaffe. High energy collisions (corresponding to thin shocks) pass through each other, after which a plasma forms in the middle, quite akin to heavyion collisions. After an initial stage of farfromequilibrium evolution the pressures become positive and are governed by hydrodynamics within a proper time 1/T, with T the local temperature at that time. In the end I will discuss recent results where we were able to perform a somewhat similar simulation for boostinvariant central collisions and matched this with recent hydrodynamic and hadronic cascade codes, which enables an interesting comparison with experimental transverse spectra for light particles at LHC or RHIC.  31Oct2013: On Scale and Conformal Invariance in Four Dimensions
Anatoly Dymarsky (DAMTP) [Transparencies]
Abstract: I will discuss the relation between scale and conformal symmetry in unitary Lorentz invariant QFTs in four dimensions.  07Nov2013: Higherorder singletons and partially massless fields
Xavier Bekaert (Tours) [Transparencies]
Abstract:Using ambient space we develop a fully gauge and o(d,2) covariant approach to boundary values of AdS(d+1) gauge fields. It is applied to the study of (partially) massless fields in the bulk and (higherorder) conformal scalars, i.e. singletons. We prove the appropriate generalization of the FlatoFronsdal theorem on the decomposition of the tensor product of two singletons, which is in agreement with the known structure of symmetries for the higherorder wave operator. All these facts support the following generalization of the higherspin holographic duality: the O(N) model at an isotropic Lifshitz point should be dual to the theory of partially massless symmetric tensor fields described by the Vasiliev equations based on the higherorder singleton symmetry algebra.  14Nov2013: The superconformal bootstrap
Balt Van Rees (CERN) [Transparencies]
Abstract:  21Nov2013: Entanglement and Geometry in 2d CFT
Tom Hartman (IAS) [Transparencies]
Abstract: I will discuss the entanglement entropy of disjoint intervals in 2d CFTs with a large central charge. These are CFTs that could plausibly have a holographic dual. Without assuming holography, the conformal block expansion at large central charge naturally leads to emergent 3d geometries. The final answer for the entanglement entropy is universal?independent of most microscopic details of the CFT ?and agrees with the prediction from the RyuTakayanagi formula in AdS/CFT.  28Nov2013: A holomorphic anomaly in the elliptic genus
Sameer Murthy (King's College  London) [Transparencies]
Abstract: I shall discuss the elliptic genera of a class of (2,2) superconformal field theories in two dimensions with noncompact target spaces. These theories have a continuous spectra and unequal density of states for bosons and fermions. The corresponding elliptic genera are not holomorphic and have mock modular behaviour. I shall discuss these theories from the ultraviolet gauged linear sigma model point of view, and explain how the lack of holomorphicity arises from an axionic compensator field that cures the chiral anomaly in the theory.  05Dec2013: qdeforming AdS_5 x S^5 superstrings
Benoit Vicedo (University of Hertfordshire) [Transparencies]
Abstract: I will describe a procedure for constructing oneparameter integrable deformations of integrable sigmamodels. In the case of the principal chiral model on G one recovers the YangBaxter sigmamodel which coincides with the squashed 3sphere sigmamodel when G = SU(2). When applied to the symmetric space sigmamodel on F/G we obtain a new oneparameter family of integrable sigmamodels. The classical symmetry algebra of the latter is a qdeformation of the symmetries of the symmetric space sigmamodel. This procedure generalises also to semisymmetric space sigmamodels. We use it to construct an integrable deformation of the AdS_5 x S^5 superstring.
 17Jan2013: Holomorphic blocks in 3 dimensions
 2012:
Lent 19Jan2012: Moduli Stabilisation for Chiral Global Models
Michele Cicoli (ICTP)
[Transparencies]
Abstract: I shall show how to combine moduli stabilisation and SU(5) or MSSM like chiral models in a fully consistent global setup in Type IIB /Ftheory by considering compactifications on CalabiYau orientifolds which admit an explicit description in terms of toric geometry. I shall present explicit choices of brane setups and fluxes which lead to three different phenomenological scenarios: the first with GUT scale strings and TeVscale SUSY ; the second with an exponentially large value of the internal volume and TeVscale SUSY without finetuning the background fluxes; and the third with a very anisotropic configuration that leads to TeVscale strings and two micronsized extra dimensions. The fibred structure of the CalabiYau threefold is also particularly suitable for cosmological purposes.  28Jan2012: Singularity structure and massless dyons of pure N=2, d=4 theories with SU(r+1) and Sp(2r) gauge groups
Jihye Seo (McGill University)
[Transparencies]Notice: special place Seminar Room 1, Isaac Newton Institute
Abstract: We study pure SeibergWitten theories with SU(r+1) and Sp(2r) gauge groups with no flavors. We study singularity loci of moduli space of the SeibergWitten curve. Using exterior derivative and discriminant operators, we can find ArgyresDouglas 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 ArgyresDouglas loci. We show that BPS charges of the massless dyons jump as we go across ArgyresDouglas loci, giving an explicit example of ArgyresDouglas loci living inside the wall of marginal stability.  01Mar2012: FluidGravity Duality at a Cutoff Surface
Cindy Keeler (U. Michigan)
[Transparencies]Notice: special place Seminar Room 1, Isaac Newton Institute
Abstract: We show by explicit construction that for every solution of the incompressible NavierStokes equation in $p+1$ dimensions, there is a uniquely associated "dual" solution of the vacuum Einstein equations in $p+2$ dimensions. We consider both a "nearhorizon" limit in which $\Sigma_c$ becomes highly accelerated, and a longwavelength hydrodynamic limit. We show that the nearhorizon expansion in gravity is mathematically equivalent to the hydrodynamic expansion in fluid dynamics, and the Einstein equation reduces to the incompressible NavierStokes equation.  08Mar2012: TBA
Kyriakos Papadodimas (CERN)
[Transparencies]
Abstract: TBA.  22Mar2012: The Harmony of Superstring Disk Amplitudes
Oliver Schlotterer (MPI Munich)
[Transparencies]
Abstract: I will present the open string tree level amplitude of massless states to any number of external legs. It turns out that the kinematic factor of disk amplitudes is entirely captured by the underlying SYM field theory, i.e. that all the dependence on polarization vectors enters through color ordered SYM amplitudes. Moreover, the structure of the N point string theory amplitude exploits the minimal basis of (N3)! SYM subamplitudes and adjoins a dual basis of (N3)! hypergeometric functions encoding the alpha' corrections. These patterns within disk amplitudes exhibit rich implications from and to field theory.The pure spinor formalism is the crucial tool to identify SYM amplitudes within the string computation. That is why I introduce a compact representation for N point SYM amplitudes in pure spinor superspace. It reflects the decomposition into cubic diagrams a la Bern, Carrasco, Johansson and generalizes Berends Giele recursion relations.

Easter 26Apr2012: Time Evolution of Entanglement Entropy
Matthew Roberts (New York University)
[Transparencies]
Abstract: We calculate the time evolution of the entanglement entropy in a 1+1 CFT with a holographic dual when there is a localized leftmoving packet of energy density. We find the gravity result agrees with a field theory result derived from the transformation properties of Renyi entropy. We are able to reproduce behavior which qualitatively agrees with CFT results of entanglement entropy of a system subjected to a local quench. In doing so we construct a finite diffeomorphism which tales threedimensional antide Sitter space in the Poincare patch to a general solution, generalizing the diffeomorphism that takes the Poincare patch a BTZ black hole. We briefly discuss the calculation of correlation functions in these backgrounds and give results at large operator dimension.  17May2012: Cusp Anomalous Dimension in N=4 Super YangMills from Integrability
Diego Correa (IFLP, Universidad Nacional de La Plata)
[Transparencies]
Abstract:  31May2012: OneLoop Renormalization and the Smatrix
David Mcgady (Princeton University)
[Transparencies]
Abstract: In this talk, I will discuss the proportionality between tree amplitudes and the ultraviolet divergences in their oneloop corrections in YangMills and (N < 4) Super YangMills theories in fourdimensions. From the point of view of local perturbative quantum field theory, i.e. Feynman diagrams, this proportionality is straightforward: ultraviolet divergences at looplevel are absorbed into coefficients of local operators/interaction vertices in the original treeamplitude. Ultraviolet divergences in loop amplitudes are also calculable through onshell methods. These methods ensure manifest gaugeinvariance, even at looplevel (no ghosts), at the expense of manifest locality. From an onshell perspective, the proportionality between the ultraviolet divergences the tree amplitudes is thus not guaranteed. I describe systematic structures which ensure proportionality, and their possible connections to other recent developments in the field.

Michaelmas 04Oct2012: The ABCDEFG of Instantons
Jaewon Song (Caltech) [Transparencies]
Abstract: We will discuss methods of computing instanton partition functions for arbitrary gauge groups including the exceptional ones. Even though there is no explicit algebraic construction of instanton moduli space available for the exceptional groups, we're able to evaluate the partition function using the blowup recursion relations derived by Nakajima and Yoshioka. We compare this result with the proposal based on the superconformal index of SCFTs with E6, E7 global symmetry. We also compare our result with the norm of certain coherent states of Walgebras and thereby extending the AGT correspondence for pure YM theory to all gauge groups.  11Oct2012: Scale Without Conformal Invariance
Jeff Fortin (CERN) [Transparencies]
Abstract: We investigate the theoretical implications of scale without conformal invariance in quantum field theory. We argue that the RG flows of such theories correspond to recurrent behaviors, i.e. limit cycles or ergodicity. We discuss the implications for the atheorem and show how dilatation generators do generate dilatations.  18Oct2012: Quarkonium dissociation by anisotropy in a strongly coupled CFT
Mariano Chernicoff (DAMTP, U. Cambridge) [Transparencies]
Abstract: We compute the screening length for heavy mesons moving through an anisotropic, strongly coupled N=4 super YangMills plasma by means of its gravity dual. We present the results for arbitrary velocities and orientations of the mesons, as well as for arbitrary values of the anisotropy. For generic motion we find that: (i) mesons dissociate above a certain critical value of the anisotropy, even at zero temperature; (ii) there is a limiting velocity for mesons in the plasma, even at zero temperature; (iii) in the ultrarelativistic limit the screening length scales as $(1v^{2)}{\epsilon}$ with $\epsilon =1/2$, in contrast with the isotropic result $\epsilon =1/4$.  25Oct2012: SCAPEZILLA: the backreaction of antibranes in flux compactifications
Iosif Bena (Saclay) [Transparencies]
Abstract: I will discuss the backreaction of antiD3 branes in geometries with D3 brane charge dissolved in fluxes, and I will show that these solutions must have a certain singularity in the infrared. Since singular solutions must normally be discarded unless there is a compelling physical reason to accept the singularity, I will discuss possible mechanisms for its resolutions, and show that none work. If this singularity is not physical this will imply that the mechanism for uplifting AdS vacua (which are ubiquitous in flux compactifications of string theory) to dS vacua by placing antibranes does not work, and hence string theory does not have a landscape of dS vacua.  01Nov2012: Partition function of N=(2,2) gauge theories on S^2 and vortices
Stefano Cremonesi (Imperial College, London) [Transparencies]
Abstract: I will review the basics of rigid supersymmetry on curved spacetimes and of supersymmetric localisation and apply these methods to 2d N=(2,2) supersymmetric field theories of vector and chiral multiplets with a vector U(1) Rsymmetry on the round 2sphere. I will explain two different localisation schemes, leading to the ``Coulomb branch'' and ``Higgs branch'' representations of the partition function. Finally, I will briefly overview the potential of these exact results for the study of type II string compactifications, geometry and supersymmetric gauge theories in various dimensions.  08Nov2012: New Skins for an Old Ceremony: The Conformal Bootstrap and the Ising Model
Sheer ElShowk (Saclay) [Transparencies]
Abstract: The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and OPE coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the Extremal Functional Method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the 2d Ising model based solely on the dimension of a single scalar quasiprimary ? no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs (such as the 3d Ising model) in the near future.  15Nov2012: Probing higher spin black holes
Eric Perlmutter (DAMTP, U. Cambridge)[Transparencies]
Abstract: I will discuss recent progress in understanding higher spin black holes and their interactions with scalar fields, in the context of Vasiliev's 3d theory of higher spin gravity. This is relevant for the holographic duality with a certain class of 2d minimal model CFTs, proposed by Gaberdiel and Gopakumar. Despite unusual aspects of causality in higher spin gravity, the behavior of scalar boundary correlators in the black hole background appears consistent with a conventional black hole interpretation.  22Nov2012: Stars, black holes and superconductors
Simon Gentle (Durham U.) [Transparencies]
Abstract: Charged black holes in planar AdS can be unstable to the formation of charged scalar hair. Through holography, one hopes to use this fact to uncover general principles governing unconventional superconductors. It has been shown however that the behaviour of `holographic superconductors' depends strongly on their embedding into string/Mtheory. In this talk I will discuss two aspects of this issue in which progress can be made. First I will demonstrate how the ground states of these systems may be found by blowing up stars in global AdS, then I will hunt for the instability of highest temperature in a wider consistent truncation of supergravity. Both aspects raise concerns that a new approach to the problem is needed.  29Nov2012: Unitarity and fuzzball complementarity: Alice fuzzes but may not even know it!
Borun Chowdhury (Amsterdam U.) [Transparencies]
Abstract: We investigate the recent black hole firewall argument. We argue that unitarity requires every quantum of radiation leaving the black hole to carry information about the initial state. Unitary evaporation is thus inconsistent with an informationfree horizon at every step of the evaporation process. The required horizonscale structure is manifest in the fuzzball proposal. To address the experience of an infalling observer, we argue for fuzzball complementarity. Unlike black hole complementarity and observer complementarity which postulate asymptotic observers experience a hot membrane while infalling ones pass freely through the horizon, fuzzball complementarity postulates that finegrained operators experience the details of the fuzzball microstate and coarsegrained operators experience the black hole. In particular, this implies that an infalling detector tuned to energy E \sim TH, where TH is the asymptotic Hawking temperature, does not experience free infall while one tuned to E \gg TH does.
 19Jan2012: Moduli Stabilisation for Chiral Global Models
 2011:
Lent 20Jan2011: Invariants, symmetries and divergences
Paul Howe (King's College London)
[Transparencies]
Abstract: "Supersymmetric invariants, their symmetries and various approaches to contructing them are discussed. Their role in the investigation of the onset of UV divergences is outlined. In particular, it is argued that D=4 N=8 supergravity is finite up to, and including, 6 loops."  27Jan2011: Dense matter at strong coupling and hedgehog black holes
Prem Kumar (Swansea University)
[Transparencies]
Abstract: "The thermodynamic properties of field theories at largeN with an equally large number of flavours are explored, focussing attention on the regime of low temperature and high density. At strong coupling, in the context of the D3D7 system, it is argued that in a certain limit such states could be described by "hedgehog" black hole solutions."  03Feb2011: Effective holographic theories for lowtemperature condensed matter systems
Elias Kiritsis (University of Crete and APC, Paris)
[Transparencies]
Abstract: "The IR dynamics of effective holographic theories capturing the interplay between charge density and the leading relevant scalar operator at strong coupling are analyzed. Such theories are parameterized by two real exponents (?,?) that control the IR dynamics. By studying the thermodynamics, spectra and conductivities of several classes of charged dilatonic black hole solutions that include the charge density back reaction fully, the landscape of such theories in view of condensed matter applications is characterized. Several regions of the (?,?) plane can be excluded as the extremal solutions have unacceptable singularities. The classical solutions have generically zero entropy at zero temperature, except when ?=? where the entropy at extremality is finite. The general scaling of DC resistivity with temperature at low temperature, and AC conductivity at low frequency and temperature across the whole (?,?) plane, is found. There is a codimensionone region where the DC resistivity is linear in the temperature. For massive carriers, it is shown that when the scalar operator is not the dilaton, the DC resistivity scales as the heat capacity (and entropy) for planar (3d) systems. Regions are identified where the theory at finite density is a Mottlike insulator at T=0. We also find that at low enough temperatures the entropy due to the charge carriers is generically larger than at zero charge density. The extremal solutions found are the most general scaling solutions in the IR generalizing the AdS and Liftshitz backrounds."  10Feb2011: String theory and the VeloZwanziger problem
Rakibur Rahman (Scuola Normale Superiore, Pisa)
[Transparencies]
Abstract: "The VeloZwanziger problem is the loss of (causal) propagation of a charged massive field with spin greater than one, when minimally coupled to a constant electromagnetic background. String theory, originally proposed as a theory of massive highspin particles, should spell out appropriate nonminimal terms to give a consistent description of such a system. We show that while string theory does achieve this feat, only the leading Regge trajectory fields can be exposed in isolation. We comment on the critical dimensionality, on the gyromagnetic ratio, and on some consistent dimensional reduction that can produce interesting models."  17Feb2011: Mesons as open strings in holographic QCD
Shigeki Sugimoto (IPMU, University of Tokyo)
[Transparencies]
Abstract: "We present our attempt to obtain meson spectrum from open strings in a top down approach of holographic QCD. Our main focus in this talk is on those obtained from the first and second excited massive open string modes. For example, we argue that a_{2}(1320), b_{1}(1235), ?(1300), a_{0}(1450), etc., are identified as the first excited massive open string states and ?_{3}(1690), ?_{2}(1670), etc., are identified as the second excited states. Ref: arXiv:1005.0655 (Done in collaboration with Toshiya Imoto and Tadakatsu Sakai)"  24Feb2011: The classical integrable structure of AdS/CFT
Benoit Vicedo (DESY, Hamburg)
[Transparencies]
Abstract: "The classical integrability of GreenSchwarz superstrings on AdS backgrounds relevant for the AdS/CFT correspondence relies on the existence of a Lax connection whose flatness is equivalent to the classical equations of motion. I will explain how a careful derivation of this Lax connection within the Hamiltonian framework leads to a modification of the well known BenaPolchinskiRoiban connection. Surprisingly, this new Lax connection coincides with the matter part of the pure spinor superstring Lax connection of Vallilo. We then show that the associated underlying integrable structure has a very natural description within the Rmatrix formalism. In particular, we identify the classical Rmatrix and give a simple algebraic meaning to the Zhukovksy map which plays a central role in the AdS/CFT correspondence."  03Mar2011: The Fate of GUTs
Sakura SchäferNameki (King's College London)
[Transparencies]
Abstract: "I will discuss, what constraints SUSY GUTs have to satisfy in order to arise from generic Ftheory compactifications to 4d. Surprisingly, a lot can be said quite generally, with fateful implications ..."  10Mar2011: Geometry of double field theory
Olaf Hohm (MIT, Cambridge)
[Transparencies]
Abstract: "I discuss the recently constructed socalled double field theory, which introduces in addition to the usual coordinates new "windingtype" coordinates in order to make the Tduality property of string theory manifest at the level of the lowenergy effective spacetime action. The new geometrical features which extend the Riemannian geometry underlying pure Einstein gravity are discussed."  17Mar2011: Framed BPS states, moduli dynamics, and wallcrossing
Sungjay Lee (University of Cambridge)
[Transparencies]
Abstract: "I will discuss supersymmetric low energy dynamics for BPS dyons in stronglycoupled N=2 SeibergWitten theories, and derive wallcrossing formulae thereof. For BPS states made up of a heavy core state and n probe (halo) dyons around it, I will derive a reliable supersymmetric moduli dynamics with 3n bosonic coordinates and 4n fermionic superpartners. The small parameters that control the approximation are not electric couplings but the mass ratio between the core and the probe, as well as the distance to the marginal stability wall where the central charges of the probe and of the core align. Quantizing the dynamics, we construct BPS bound states and derive the primitive and the semiprimitive wallcrossing formulae, conjectured by Denef and Moore from the first principle. I will also speculate on applications to line operators and Darboux coordinates, and also about extension to supergravity setting."  24Mar2011: Physical properties of pwave holographic superconductors
Johanna Erdmenger (Werner Heisenberg Institute, Munich)
[Transparencies not available]
Abstract: "Recently, considerable progress has been achieved in using gauge/gravity duality for describing strongly coupled systems of relevance for condensed matter physics. In this context, I discuss both topdown approaches and bottomup approaches to holographic superconductors where the order parameter has pwave symmetry. In the topdown approaches, the holographic superconductors are realized in a probe brane construction involving a probe of two Dbranes at finite isospin density. The dual field theory is known explicitly. We obtain the thermodynamics and the Fermi surface for these systems. Moreover, we consider bottomup approaches for pwave superconductors in which we study the backreaction of the required SU(2) gauge field on the geometry. We find the phase diagram. A particularly interesting feature of this model is that the shear viscosity over entropy ratio displays nonuniversal behaviour, it is temperaturedependent at leading order in N and lambda."

Easter 05May2011: Describing M5branes using loop spaces
Christian Sämann (HeriotWatt University, Edinburgh)
[Transparencies]
Abstract: "I will start by discussing a lift of the ADHM construction of monopoles, which can be interpreted in terms of a D1D3brane configuration, to a construction of selfdual strings, which is related to an M2M5brane configuration. This construction involves a loop space description of the abelian M5brane theory. I will then show that the nonabelian loop space equations correspond to a recently found set of supersymmetric equations for the (2,0) tensor multiplet in six dimensions. Therefore, they might indeed capture some aspects of the effective dymanics of multiple M5branes."  12May2011: Holographic phase space: cfunctions and black holes as renormalization group flows
Miguel Paulos (LPTHE, Paris)
[Transparencies]
Abstract: "We consider domainwall and AdSblack hole backgrounds in Lovelock theories of gravity. We construct a "cfunction" N(r) for these, which we argue counts the number of effective fields at a given scale  on AdS spaces it is related to the Euler anomaly, and at a black hole horizon it is proportional to the entropy. The monotonicity properties of N are controlled by the "gravitational field" which has opposite signs in the domainwall and black hole backgrounds, due to the presence of negative (positive) energy in the former (latter). We show how N can be written as the ratio of the Wald entropy to a quantity resembling an effective phase space volume."  19May2011: Holographic hydrodynamics on nonconformal field theories
Giuseppe Policastro (Ecole Normale Superieure, Paris)
[Blackboard talk]
Abstract: "In recent years the description of the transport properties of nonconformal field theories has attracted much attention. I will discuss some of these results, in particular concerning the phenomenological models of "improved holographic QCD" based on Einsteindilaton gravity with a potential."  26May2011: Anomalyinduced charges from Skyrme model
Takaaki Ishii (University of Cambridge)
[Transparencies not available]
Abstract: "We investigate baryons under external electromagnetic fields. We show a novel charge structure of baryons in electromagnetic field due to the chiral anomaly. Here baryons are treated as solitons of mesons, and we use Skyrmions to calculate the charge distributions in a single baryon and find an additional charge. We discuss the nonlinear pion clouds the baryons wear. Amusing charge distributions for classical multibaryons with B=2, 3,...,8 and 17 are also shown."  02Jun2011: Lessons from holography: the shear viscosity bound and UV/IR decoupling
Sera Cremonini (University of Cambridge and Texas A&M University, College Station)
[Transparencies]
Abstract: "The gauge gravity duality has proven to be a valuable tool for probing the dynamics of strongly coupled field theories. Within this program, much of the focus is now on systems which exhibit rather different UV and IR behaviors. In this talk I will discuss the role played by the gauge/gravity duality on understanding properties of the shear viscosity to entropy ratio. In particular, I will focus on theories where there is a decoupling of UV from IR physics."  09Jun2011: The complete npoint superstring disk amplitude in pure spinor superspace
Carlos Mafra (Albert Einstein Institute, Potsdam)
[Transparencies not available]
Abstract: "In this talk I'll show how the pure spinor formalism can be used to obtain a surprinsingly simple closedformula solution to all npoint superstring disk amplitudes."  16Jun2011: Holography of massdeformed M2branes
Seok Kim (Seoul National University, Seoul)
[Transparencies]
Abstract: "We study holographic aspects of M2brane CFT with mass deformations. We first show how the geometry of Lin, Lunin, Maldacena is related to the supersymmetric vacua of the field theory. We also find the holographic RG flow of a massdeformed CFT and find the Schrodinger geometry in the IR."  23Jun2011: N^{3} and junctions in 6dimensional (2,0) theories
Kimyeong Lee (Korea Institute for Advanced Study, Seoul)
[Transparencies]
Abstract: "We count the number of 1/4 BPS objects in the Coulomb phase of 6d (2,0) theories and find it is identical to onethird of their anomaly coefficient c_{G} which is product of the dimension and dual Coxeter number of the corresponding group."  12Jul2011: Differential geometry for string theory, beyond Riemann
Imtak Jeon (Sogang University, Seoul)
[Transparencies]
Notice: special date and time Tuesday, 12Jul2011, 2:15pm
Abstract: "While the fundamental object in Riemannian geometry is the metric, closed string theories put a twoform gauge field and a dilaton on the same footing as the metric. In this talk we introduce a novel differential geometry which treats those three objects in a unified manner, and manifest not only the gauge symmetries (diffeomorphism plus oneform gauge symmetry) but also the O(D,D) Tduality. We also discuss how to couple to YangMills theory."

Michaelmas 06Oct2011: Holographic Fermi Surfaces: The view from the top down
Julian Sonner (Imperial College London & University of Cambridge)
[Transparencies]
Abstract: Strongly interacting fermions at finite density are infamously hard to treat. Gauge/gravity duality gives a way of studying them in a controlled environment. For such studies to be reliable it is important that the models are eventually embedded in Mtheory (or string theory). In this talk I will describe how to look for some of the most basic features of fermionic finitedensity states in Mtheory, such as the occurrence of Fermi surfaces, and describe the wider implications of our recent intriguing results on these objects.  13Oct2011: On Renormalization Group Flows in Four Dimensions
Zohar Komargodski (IAS & Weizmann Institute of Science)
[Transparencies]
Abstract: We discuss some general aspects of renormalization group flows in four dimensions. Every such flow can be reinterpreted in terms of a spontaneously broken conformal symmetry. We analyze in detail the consequences of trace anomalies for the effective action of the NambuGoldstone boson of broken conformal symmetry. While the canomaly is algebraically trivial, the aanomaly is "nonAbelian," and leads to a positivedefinite universal contribution to the Smatrix of 2>2 dilaton scattering. Unitarity of the Smatrix results in a monotonically decreasing function that interpolates between the Euler anomalies in the ultraviolet and the infrared, thereby establishing the atheorem.  20Oct2011: Aspects of Holographic Fermions
Joao Laia (University of Cambridge)
[Transparencies]
Abstract: We show how to compute beta functions for double trace fermionic operators in the dual conformal field theory. We also describe a novel implementation of nonrelativistic fermions in AdS/CFT by imposing Lorentz violating boundary terms for a Dirac spinor in AdS4. The dual boundary theory is scale invariant, and can be reached by an RG flow started by a Lorentz violating double trace perturbation. This new CFT exhibits a number of interesting properties, including a dispersionless flat band of gapless excitations.  24Oct2011: Instantons from Branes and Higgs Vacua in N=1 Theories
Anatoly Dymarsky (IAS)
[Transparencies]
Notice: special date and time Monday, 24Oct2011, 4:00pm
Abstract: We study vacua of N=1 SUSY gauge theory using conventional field theory tools and a dual supergravity background. The Higgs vacua are dual to mobile D3branes which dissolve into flavor D7branes. Hence the moduli space of the worldvolume gauge instantons on D7branes should match the Higgs branch of the field theory. In case of N=2 theories this relation was readily provided by the ADHM construction. In the N=1 case both sides of the duality are more complicated because of quantum corrections. We carefully analyze the case of the cascading N=1 SU(N+M)xSU(N) theory and find agreement between field theory and gravity.  27Oct2011: Fluid/gravity at finite "r"
Daniel Brattan (Durham University)
[Transparencies]
Abstract: In this talk I will review my recent paper, arXiv:1106.2577, which gives the dual field theory formulation of the Dirichlet problem for gravity in the bulk. I will highlight some rather surprising results and the still open questions they pose.  03Nov2011: Matrix models, duality and spontaneous SUSY breaking in 3D QFT
Vasilis Niarchos (University of Crete)
[Transparencies]
Abstract: I will discuss recent developments in threedimensional superconformal field theories based on the use of localization techniques. Special emphasis will be given to a particular example of threedimensional Seiberglike duality and the proposal of a new nonperturbative constraint on spontaneous supersymmetry breaking based on matrix models.  10Nov2011: Holographic threepoint functions for short operators
Joseph Minahan (Uppsala University)
[Transparencies]
Abstract: "TBA."  17Nov2011: On the Taxonomy of Holographic Fermi/NonFermi Liquids
Norihiro Iizuka (CERN)
[Transparencies]
Abstract: The existence of NonFermi liquids which are not described by Landau?s Fermi liquids is a fascinating puzzle in theoretical physics. In this talk, I will show universal field theories where we can go around the Landau?s Fermiliquids and obtain NonFermiLiquid behavior. These field theories contain dynamical singlet fermions which couple through fermion bilinear terms to strongly coupled sectors which are characterized by its dynamical scaling. Suppose these strongly coupled sectors have gravity dual (which is not necessarily antide Sitter space), then by using powerful gauge/gravity duality, I will argue how these dynamical scaling parameters determine the natures of the dynamical singlet fermions in a very universal way; These natures include the existence of Fermi/NonFermi liquids, sharp Fermisurface, the decay rates and breakdown of the quasiparticles description. I will end with discussion for generalization of our work to include the lattice effects and impurities for more interesting condensed matter system.  24Nov2011: Holography of EinsteinMaxwellDilaton theories and applications to Condensed Matter Systems
Blaise Gouteraux (Universite Paris 7)
[Transparencies]
Abstract: Recently, holographic techniques have been applied to Condensed Matter Systems (CMS) with stronglycoupled electrons. EinsteinMaxwellDilaton (EMD) theories provide an interesting setup for such endeavours, as they allow nontrivial, nonconformal InfraRed fixed points, which are postulated to be Quantum Critical (QC) points describing the physics near extremality. First, we shall describe the black hole solutions of EMD theories and review earlier results on their transport coefficients. Then, we shall address the issue of how to set holography up for these theories, using 'generalised' dimensional reduction. Finally, we shall apply this to the previously mentionned QC points.  01Dec2011: kString Tension from EguchiKawai Reduction
Daniele Dorigoni (University of Cambridge)
[Transparencies]
Abstract: The kstring can be thought of as a bound state of k fundamental QCDstrings. Its tension has been vastly discussed in the literature. In particular, most analytic approaches in the case of theories with adjoint fermions suggest that the kstring tension respect the Sine scaling. After having introduced some basic facts about kstring I will discuss how the use of EguchiKawai dimensional reduction can help us in computing the tension. As an explicit example I will discuss in details the reduction of adjointQCD from 3 to 2 dimensions in which the kstring tension can be computed under some assumptions, whose validity I will analyse.  08Dec2011: Spinning Conformal Correlators and Blocks
Slava Rychkov (Ecole Normale Superieure)
[Transparencies]
Abstract: We will talk about recent progress in using embedding space formalism to describe conformally invariant correlation function of operators with spin.  15Dec2011: Bosonic Excitations in Holographic Quantum Liquids
Richard Davidson (University of Oxford)
[Transparencies]
Abstract: I will discuss the bosonic excitations present in certin stronglyinteracting holographic field theory states with a large density of matter. Particular attention will be paid to the properties of the sound modes of these theories and how they compare with the properties of the sound mode of a LandauFermi liquid.
 20Jan2011: Invariants, symmetries and divergences
 2010:
Lent 14Jan2010: Surprising symmetry of scattering amplitudes in gauge theories
Gregory Korchemsky (CEA Saclay)
[Transparencies]
Abstract: "I will review a recent progress in computing scattering amplitudes in gauge theories  a fascinating subject which has been recently boosted by the formulation of the gauge/string duality in maximally supersymmetric YangMills theory. In addition to the conventional symmetry of the underlying Lagrangian, the scattering amplitudes in this theory exhibit a new, dual superconformal symmetry. This symmetry is powerful enough to completely determine the scattering amplitudes for arbitrary coupling in a suitably defined limit."  21Jan2010: Inching towards strange metallic holography
David Tong (University of Cambridge)
[Transparencies]
Abstract: "Strange metals are materials with numerous anomalous properties. The flow of electricity within these materials cannot be explained in the familiar language of a fluid of individual electrons, but instead requires a new strongly interacting description. In this talk, I will review some basic facts about these materials. With this as motivation, I will explain how to compute conductivity in certain strongly interacting, nonrelativistic field theories which are defined holographically by gravity in Lifshitz backgrounds."  28Jan2010: Tduality invariant string theory at the quantum level
Daniel Thompson (Queen Mary, University of London)
[Transparencies]
Abstract: "In this talk I will be discussing some reformulations of string theory which promote Tduality to the level of a manifest symmetry namely Hull's Doubled Formalism and Klimcik and Severa's PoissonLie Tduality. Such formalisms double the number of fields but also incorporate some chiralitylike constraint. Invoking this constraint leads one to consider sigmamodels which though duality invariant do not possess manifest Lorentz Invariance. Whilst such formalisms make sense at a classical level their quantum validity is less obvious. I address this issue by examining the renormalization of these duality invariant sigma models. This talk is based upon both forthcoming work and recent work: arXiv:0910.1345 [hepth] and its antecedents arXiv:0708.2267 [hepth], arXiv:0712.1121 [hepth]."  04Feb2010: Gradient formula for the beta function of 2d quantum field theory
Anatoly Konechny (HeriotWatt University, Edinburgh)
[Transparencies]
Abstract: "A gradient formula is proven of the form ?_{i}c = (g_{ij} + ?g_{ij}b_{ij})?^{j} where ?^{j} are the beta functions, c and g_{ij} are the Zamolodchikov cfunction and metric, b_{ij} is an antisymmetric tensor introduced by H. Osborn and ?g_{ij} is a certain metric correction. The formula is derived under the assumption of stressenergy conservation and certain conditions on the infrared behaviour. Being specialized to nonlinear sigma models this formula implies a onetoone correspondence between renormalization group fixed points and critical points of c."  11Feb2010: Towards exact quantum entropy of black holes
Atish Dabholkar (LPTHE, Paris)
[Transparencies]
Abstract: "I will report on some recent progress on defining and computing finite size effects in the entropy of black holes with highly nontrivial agreements between thermodynamics and statistical mechanics. I will describe a number of puzzles and their resolutions along with some exact computations, and then briefly discuss the role of mock modular forms and BorcherdsKacMoody superalgebras in this context."  18Feb2010: Magnetic bags and black holes
Stefano Bolognesi (University of Cambridge)
[Blackboard talk]
Abstract: "We begin with a review of magnetic bags, which are macroscopic limit of multimonopoles with large magnetic flux. We focus on some of their common properties with black holes. We then add gravity to the system, and study the transition from monopole to black hole."  25Feb2010: Viscosity and conductivity in general theories of gravity
Miguel Paulos (University of Cambridge)
[Transparencies]
Abstract: "Recently there has been great interest in calculating transport coefficients for field theories at large coupling, using AdS/CFT. In this talk I will discuss recent work showing how to use the membrane paradigm to easily compute the shear viscosity and conductivity in arbitrary gravity theories. In a certain sense these can be thought of as effective couplings at the black hole horizon dual to the field theory plasma. An explicit Waldlike formula for these couplings is given for a large class of generalized gravity theories."  04Mar2010: Brane tilings, M2branes and ChernSimons theories
Noppadol Mekareeya (Imperial College London)
[Transparencies]
Abstract: "Brane tilings are known to describe the largest known class of SCFTs in 3+1 dimensions. There is a well established formalism to find AdS_{5} x SE_{5} duals to these SCFTs and to compare results on both sides. This talk extends this formalism to 2+1 dimensional SCFTs, living on the worldvolume of M2branes, which are dual to AdS_{4} x SE_{7} backgrounds of Mtheory. The SCFTs are quiver gauge theories with 4 supercharges (N=2 in 2+1 dimensions) and ChernSimons couplings. They admit a moduli space of vacuum configurations which is a CY_{4} cone over SE_{7}. The talk will go over the formalism and look at several examples in detail."  11Mar2010: Connections between dualities of string theory and the ultraviolet properties of maximal supergravity
Michael Green (University of Cambridge)
[Transparencies]
Abstract: "This talk will present a forensic analysis of the first few terms in the low energy expansion of the type II superstring four graviton amplitude in dimensions 3?D?10. Terms in this expansion are automorphic functions of the moduli that are invariant under the duality groups in the E_{n} series (1?n?8). In particular, they are expressed in terms of Langlands Eisenstein series and generalisations that possess some very surprising properties. The coefficients of logarithmic ultraviolet divergences of maximal supergravity are encoded in the structure of these functions and emerge as a consequence of the dualities. This suggests that there is a sevenloop divergence in N=8 supergravity in four dimensions."  18Mar2010: 3d N=2 CFTs with chiral flavours from M2branes at toric CY_{4} singularities
Stefano Cremonesi (TelAviv University)
[Transparencies]
Abstract: "Following the work of Aharony, Bergman, Jafferis and Maldacena, a great effort has been made to understand the 3d conformal gauge theories describing M2branes at conical singularities. Special attention has been directed to N=2 supersymmetric AdS_{4}/CFT_{3} pairs arising from M2branes at toric CY 4folds, where powerful algebraic techniques are available. After reviewing known results concerning brane tilings, the relation between the toric CY_{3} and CY_{4} moduli spaces of 4d and 3d toric quiver gauge theories, and Mtheory/type IIA duality, I will explain how fundamental flavours naturally arise in this framework, and how their matter content and superpotential couplings to bifundamental fields are encoded in geometric data. Quantum effects are crucial in determining the moduli spaces of such flavoured quiver gauge theories. Quiver ChernSimons (CS) theory of the kind considered in the AdS_{4}/CFT_{3} literature so far can be obtained by coupling a 3d gauge theory with the same quiver diagram but no CS terms to chiral flavours, and integrating the latter out via a real mass term."

Easter 22Apr2010: Phenomenology of Dbranes at toric singularities
Sven Krippendorf (University of Cambridge)
[Transparencies]
Abstract: "In this talk I will discuss aspects of Dbrane model building at toric singularities. After reviewing dimer techniques, I will apply these tools to show an upper bound on the number of families and discuss why the lightest quark is massless in this infinite class of models. We compute the CKM matrix for explicit models in this setting and find the singularities possess sufficient structure to allow for realistic mixing between generations and CP violation. This talk is based on arXiv:1002.1790."  29Apr2010: Pohlmeyer reduction for AdS_{5} x S^{5} superstring
Arkady Tseytlin (Imperial College London)
[Transparencies]
Abstract: "We shall review several aspects of Pohlmeyer reduction applied to AdS_{5} x S^{5} superstring. We shall discuss the treelevel Smatrix for the elementary excitations of the reduced theory and compare it to the Smatrix of the superstring theory."  06May2010: Fluxes, geometries and nongeometries
Savdeep Sethi (University of Chicago)
[Transparencies]
Abstract: Not available  13May2010: N=8 and N=6 superspace constraints for threedimensional gauge theories
Robert Wimmer (Ecole Normale Superieure, Lyon)
[Transparencies]
Abstract: "We present a systematic analysis of the N=8 and N=6 superspace constraints in three spacetime dimensions. The general coupling between vector and scalar supermultiplets is encoded in an SO(8) tensor for the N=8 and an SU(4) tensor for the N=6 case. These tensors are functions of the matter superfields and are subject to a set of algebraic and superdifferential relations. We show how conformal BLG and ABJM models, which describe the dynamics of M2 branes in Mtheory, as well as the threedimensional super YangMills theory provide solutions to these constraints and can both be formulated in this universal framework. We also discuss the supersymmetry enhancement from N=6 to N=8 via monopole operators."  20May2010: SUSY gauge theories and quantum many body systems
Samson Shatashvili (Trinity College, Dublin and IHES, BuressurYvette)
[Transparencies]
Abstract: "I review recent results on the relation between supersymmetric vacua and quantum integrability."  27May2010: Heterotic moduli space via linear sigma models
Ilarion Melnikov (Albert Einstein Institute, Potsdam)
[Blackboard talk]
Abstract: "The linear sigma model is particularly adept at describing an interesting subset of heterotic moduli. Recently these deformations were studied for mirror pairs of CalabiYau hypersurfaces in toric varieties. This led to an identification of mirror symmetric (0,2) linear sigma models, as well as a construction of an explicit mirror map. I will discuss these developments and their significance for our understanding of the heterotic string."  03Jun2010: Amplitudes using pure spinors
Jonas Bjornsson (University of Cambridge)
[Transparencies]
Abstract: "A first quantised approach to loop amplitudes based on the pure spinor particle is applied to the systematics of fourgraviton amplitudes in theories with maximal supersymmetry. Counting of fermionic zero modes allows the identification of momentum factors multiplying R^{4} in the low energy limit thereby making manifest their ultraviolet properties as a function of dimension, D. For L=2,3,4 loops the leading divergence is in D=4+6/L dimensions and proportional to d^{2L} R^{4}, in line with earlier field theory calculations. However, at 5 loops there is a radical change in the systematics, suggesting the presence of a contribution with an explicit logarithmic ultraviolet divergence when D=24/5 that is proportional to d^{8} R^{4}. We further argue that d^{8} R^{4} should receive contributions from all loops, which would imply that N=8 supergravity (with D=4) is not protected by supersymmetry from a sevenloop divergence."  08Jun2010: Black hole microstate counting and its macroscopic counterpart
Ashoke Sen (HarishChandra Research Institute, Allahabad)
[Transparencies]
Notice: special date and time Tuesday, 08Jun2010, 4:00pm
Abstract: "In this talk we shall describe how the near horizon geometry of an extremal black hole contains precise information about the ensemble of quantum states the black hole represents. This includes not only the total number of states in the ensemble, but also distribution of global charges among the members of the ensemble."  10Jun2010: Supersymmetry, localization and quantum entropy function
Ipsita Mandal (HarishChandra Research Institute, Allahabad)
[Transparencies]
Abstract: "AdS_{2}/CFT_{1} correspondence leads to a prescription for computing the degeneracy of black hole states in terms of path integral over string fields living on the near horizon geometry of the black hole. In this talk, I will discuss about how to make use of the enhanced supersymmetries of the near horizon geometry and localization techniques to argue that the path integral receives contribution only from a special class of string field configurations which are invariant under a subgroup of the supersymmetrytransformations. I will identify saddle points which are invariant under this subgroup. I will also use this analysis to show that the integration over infinite number of zero modes generated by the asymptotic symmetries of AdS_{2} generate a finite contribution to the path integral."

Michaelmas 07Oct2010: From correlation functions to Wilson loops and amplitudes
Burkhard Eden (Durham University)
[Transparencies]
Abstract: "We discuss a class of npoint correlation functions of 1/2 BPS operators in N=4 super YangMills theory in four dimensions. Since this is a massless theory the question is best discussed in configuration space. For generic positions of the operators these correlation functions are finite. We give a summary of recent work on the leading singular behaviour in a limit in which the positions are taken to be successively lightlike separated. In dimensional regularisation or with a mass regulator the correlation functions reduce to polygonal Wilson loops with lightlike edges. A useful technical tool is to compute the correlators by insertions of the N=2 YangMills Lagrangian, in which case it is particularly simple to take the lightlike limit. If in a nonstandard version of dimensional regularisation only the dimension of the integration measure at the insertion points is modified, we reproduce scattering amplitudes instead. The integrand obtained in this way exactly agrees with a recent proposal by ArkaniHamed et al."  14Oct2010: Scaling and integrability from AdS_{5} x S^{5}
Riccardo Ricci (Imperial College London)
[Transparencies]
Abstract: "According to AdS/CFT a remarkable correspondence exists between strings in AdS_{5} x S^{5} and operators in N=4 SYM. A particularly important case is that of fastspinning folded closed strings and the so called twistoperators in the gauge theory. This is a remarkable tool for uncovering and checking the detailed structure of the AdS/CFT correspondence and its integrability properties. In this talk I will show how to match the expression of the anomalous dimension of twist operators as computed from the quantum superstring with the result obtained from the Bethe ansatz of SYM. This agreement resolves a longstanding disagreement between gauge and string sides of the AdS/CFT duality and provides a highly nontrivial strong coupling test of SYM integrability."  21Oct2010: The classical geometry of quantum integrability
Nikita Nekrasov (IHES, BuressurYvette)
[Transparencies]
Abstract: "Supersymmetric gauge theories give rise to a plethora of quantum integrable systems, and to a construction of the spectra of the latter. In some cases the gauge theory construction is equivalent to the Bethe ansatz techniques, in the form of the Bethe equations written in terms of the YangYang functional. We explain the meaning of this functional (which puzzled the experts in the field for the last forty years) using the branes in the gauge theory. An important ingredient of our construction in the case of Hitchin system is the new set of Darboux coordinates on the moduli space of flat SL(2,C) connections."  28Oct2010: Mesons in the (Dymarsky)KupersteinSonnenschein holographic models
Matthias Ihl (Universidade Federal do Rio de Janeiro)
[Transparencies]
Abstract: "I will first discuss some new results concerning the phenomenology of pions and vector mesons in a model of flavor chiral symmetry breaking in the KlebanovWitten background, recently introduced by Kuperstein and Sonnenschein. I will outline the calculation of electromagnetic form factors in this model. Here, our main result is the pion form factor, which matches available experimental data surprisingly well. In the second part of the talk, I will present our results and discuss ongoing research relating to the spectra of scalar and vector mesons in the DymarskyKupersteinSonnenschein model, which geometrically realizes flavor chiral symmetry breaking in the KlebanovStrassler model, i.e. a nonconformal deformation of the KlebanovWitten background. Interestingly, the lightest scalar meson, associated with fluctuations of the background gauge field, is lighter than the lightest vector meson in this model, which potentially has interesting implications for holographic nuclear physics."  04Nov2010: Double field theory and the geometry of duality
Chris Hull (Imperial College London)
[Transparencies]
Abstract: "String theory on a torus requires the introduction of dual coordinates conjugate to string winding number. For a dtorus, string theory can be formulated in terms of an infinite tower of fields depending on both the d torus coordinates and the d dual coordinates. This talk focuses on a finite subsector consisting of a metric and bfield (both d x d matrices) and a dilaton all depending on the 2d doubled torus coordinates. The double field theory is constructed and found to have a novel symmetry that reduces to diffeomorphisms and antisymmetric tensor gauge transformations in certain circumstances. It also has manifest Tduality symmetry which provides a generalisation of the usual Buscher rules to backgrounds without isometries. The theory has a real dependence on the full doubled geometry: the dual dimensions are not auxiliary. It is concluded that the doubled geometry is physical and dynamical."  11Nov2010: From weak to strong coupling in ABJM theory
Marcos Marino (Geneva University)
[Transparencies]
Abstract: "It has been recently pointed out that the partition function and Wilson loop vevs in ABJM theory can be computed by a matrix model. By relating it to a topological string theory, we solve this matrix model at all orders in the 1/N expansion. We show that the planar limit gives explicit, exact interpolating functions of the 't Hooft coupling which make it possible to test various gravity predictions for the strong coupling behavior of ABJM theory. We give in particular the first gauge theory derivation of the N^{3/2} growth in the degrees of freedom typical of N M2branes. We also use the explicit results on the allgenus expansion of the partition function to address nonperturbative aspects of the type IIA superstring in AdS_{4} backgrounds, like Borel summability and the role of Dbrane instantons."  18Nov2010: Generalized geometry and Mtheory
David Berman (Queen Mary, University of London)
[Transparencies not available]
Abstract: "We will show how one can naturally reformulate (the bosonic part of) eleven dimensional supergravity using generalized geometry so that the duality group becomes a manifest symmetry. The relation to Tduality for Membranes is discussed along with futher details on the symmetries of Mtheory."  25Nov2010: Quantum Riemann surfaces
Tudor Dimofte (University of Cambridge)
[Blackboard talk]
Abstract: "Quantized complex curves (Riemann surfaces) play a central role in many areas of mathematical physics, including topological string theory, ChernSimons theory with noncompact gauge group, and irrational conformal field theory (as relevant, in particular, for the AGT correspondence). In all these cases, the quantum curves yield operators that annihilate partition functions. However, for the most part, the actual quantization of these curves has only been understood indirectly. I will discuss a geometric, intrinsic quantization scheme in the context of ChernSimons theory that has promise of extending to full generality."  02Dec2010: Elliptic hypergeometric integrals, superconformal indices and duality
Viacheslav Spiridonov (LTP JINR, Dubna)
[Transparencies]
Abstract: "Around ten years ago the speaker has introduced a new class of special functions of mathematical physics  the elliptic hypergeometric integrals. Some of these integrals are either exactly computable or have highly nontrivial symmetry transformations. In 2008, Dolan and Osborn have discovered that superconformal indices of supersymmetric field theories are expressed in terms of such integrals. Equalities of the indices in a number of Seiberg dual field theories follow from the properties of the integrals which were rigorously established earlier. In a joint work with G. Vartanov we have conjectured many new mathematical identities following from known dual field theories and, vice versa, many new supersymmetric dualities were suggested from known relations for elliptic hypergeometric integrals. In this talk the structure of the indices and corresponding integrals will be described and a brief summary of our results will be given."  09Dec2010: Fermionic Tduality from a spacetime perspective
Hadi Godazgar (University of Cambridge)
[Transparencies]
Abstract: "We consider the lowenergy target space theory and show that the type II supergravity equations admit a symmetry that transforms the RamondRamond fields and the dilaton. The transformations given by this symmetry involve Killing spinors and include the transformations of fermionic Tduality. However, we show that they also allow real transformations."  16Dec2010: Travelling front of the decaying brane
Debashis Ghosal (Jawaharlal Nehru University)
[Transparencies]
Abstract: "Some of the perturbative vacua of open string theory are known to be unstable. They decay to other (meta)stable vacua. We will consider the dynamics of this relaxation process (decay). In particular, the equation that describes an inhomogeneous decay turns out to be a variant of a nonlinear partial differential equation that appears in many other areas. We will point out their similarities and differences."
 14Jan2010: Surprising symmetry of scattering amplitudes in gauge theories
 2009:
Lent 15Jan2009: Black hole microstate geometries and the information paradox
Iosif Bena (CEA, Saclay)  22Jan2009: Wilson loops in N=6 supersymmetric Chern Simons theory
Donovan Young (Humboldt University, Berlin)  29Jan2009: 4loop perturbative gauge theory results from AdS/CFT
Romuald Janik (Jagiellonian University, Krakow)  05Feb2009: Jet quenching in heavy ion collisions from AdS/CFT
Jose Edelstein (University of Santiago de Compostela)  12Feb2009: NonAbelian vortices in N=1* theory and its gravity dual
Prem Kumar (University of Swansea)  19Feb2009: Superprotected npoint functions in N=4 super YangMills
Jan Plefka (Humboldt University, Berlin)  26Feb2009: Temperature versus acceleration: The Unruh effect for holographic models
Kasper Peeters (University of Durham)  05May2009: Computing Hermitian YangMills connections
Volker Braun (Dublin Institute for Advanced Studies)  12May2009: Scattering amplitudes in supersymmetric ChernSimons theory
Tristan McLoughlin (Albert Einstein Institute, Potsdam)

Easter 23Apr2009: Simplifications of unordered amplitudes in gravity and QED
N. Emil J. BjerrumBohr (Niels Bohr Institute, University of Copenhagen)  30Apr2009: The Kerr/CFT correspondence
Monica Guica (LPTHE, University Pierre et Marie Curie)  07May2009: Twistor methods for scattering amplitudes
David Skinner (University of Oxford)  14May2009: Integrability for the full planar spectrum of AdS/CFT
Pedro Vieira (Albert Einstein Institute, Potsdam)  21May2009: SU(N) flux tubes as NambuGoto strings
Andreas Athenodorou (University of Oxford)  28May2009: Holographic superconductors
Julian Sonner (Imperial College London and Trinity College Cambridge)  04Jun2009: Supersymmetry breaking in local string/Ftheory models
Sven Krippendorf (University of Cambridge)  11Jun2009: Spiky strings and spin chains
Manuel Losi (University of Cambridge)

Michaelmas 08Oct2009: Gauge threshold corrections for local string models
Joseph Conlon (University of Oxford)
[Blackboard talk; Transparencies of a CERN seminar]
Abstract: "Local string models are those where Standard Model degrees of freedom arise on a small region inside a large bulk volume. I study threshold effects on gauge coupling running for such models. The KaplunovskyLouis formula for locally supersymmetric gauge theories predicts the unification scale should be the bulk winding mode scale, parametrically large than the string scale where divergences are naively cut off. Analysis of explicit string models on orbifold/orientifold geometries confirms this; the winding mode scale arises from the presence of tadpoles uncancelled in the local model. I briefly discuss phenomenological applications to supersymmetry breaking and gauge coupling unification."  15Oct2009: Universal phenomena in strongly coupled gauge theories and gravity
Ayan Mukhopadhyay (HarishChandra Research Institute, Allahabad)
[Transparencies]
Abstract: "The AdS/CFT correspondence defines a sector with universal strongly coupled dynamics in the field theory as the dual of pure gravity in AdS described by Einstein's equation with a negative cosmological constant. We will explain, from the fieldtheoretic viewpoint how the dynamics in this sector gets determined by the expectation value of the energymomentum tensor alone. We will first show that the Boltzmann equation has very special solutions which could be functionally completely determined in terms of the energymomentum tensor alone. We will call these solutions 'conservative' solutions. We will indicate why conservative solutions should also exist when we refine this kinetic description to go closer to the exact microscopic theory or even move away from the regime of weak coupling so that no kinetic description could be employed. We will argue that these 'conservative solutions' form the universal sector dual to pure gravity at strong coupling and large N. Based on this observation, we will propose a 'regularity conditon' on the energymomentum tensor so that the dual solution in pure gravity has a smooth future horizon. We will also study if irreversibility emerges only at long time scales of observation, unlike the case of the Boltzmann equation."  22Oct2009: Making contact with supersymmetric AdS_{5} solutions
Jerome Gauntlett (Imperial College London)
[Transparencies]
Abstract: "We discuss the most general class of supersymmetric conformal field theories in four spacetime dimensions that have a D=5 antideSitter (AdS) dual in type IIB supergravity. We discuss the underlying geometry and show that there is a canonical contact structure which can be used to calculate quantities of physical interest, such as the central charge of the conformal field theory, without full knowledge of the solution."  29Oct2009: Dynamical vacuum selection in string theory
Jock McOrist (University of Cambridge)
[Transparencies]
Abstract: "Intersecting brane models in string theory are known to exhibit a rich landscape of vacua. Within a particular class of models, I will describe how early universe cosmology generically drives the system to a particular long lived metastable vacuum. These results are of relevance to the landscape problem in string theory."  05Nov2009: Transport in QGP and noncritical holography
Umut Gürsoy (University of Utrecht)
[Transparencies]
Abstract: "I will present a phenomenological model of the quarkgluon plasma that stems from 5dimensional holography. The model is superior to the previous 5D models as it incorporates the running of the gauge coupling. It is constructed by requirements from QCD and a few lattice data. I will describe the transport properties of the quarkgluon plasma such as the bulk viscosity, energy loss of heavy quarks etc and their effects on the observables."  12Nov2009: Wilson loops: From pseudoholomorphic surfaces to 2d YangMills
Riccardo Ricci (Imperial College London)
[Transparencies]
Abstract: "In this talk, I will discuss a new family of supersymmetric Wilson loop operators in N=4 SYM. These operators can be defined for any loop on a threesphere in spacetime and generically preserve two superconformal charges. On the string side, via AdS/CFT duality, these loops map to surfaces which are 'pseudoholomorphic' with respect to a novel almostcomplex structure defined on a suitable subspace of AdS_{5}xS^{5}. Of particular interest is the subclass of loops lying on a twosphere in spacetime whose expectation value is conjectured to be computed exactly in terms of the analogous observables in bosonic 2d YangMills on S^{2}. Several evidences for this conjecture, both on the gauge theory and on the string theory side will be discussed."  19Nov2009: Twisted tori and flux backgrounds of type II and heterotic string theory
David Andriot (LPTHE, Paris)
[Transparencies]
Abstract: "Solvmanifolds, in particular nilmanifolds, commonly known as twisted tori, provide several examples of internal manifolds in flux compactifications towards de Sitter, Minkowski or Anti de Sitter. The properties of these manifolds, their relation to the sixdimensional torus, and the string vacua obtained on them are the main interests of this talk. We will first present some properties of these manifolds. We will give a generic construction of their MaurerCartan forms out of the sixdimensional torus, via a transformation called the twist. This transformation actually encodes most the properties of these manifolds, in particular their compactness. We will then describe several Minkowski flux backgrounds of type II supergravity obtained on these manifolds. Thanks to the generalized complex geometry approach, we will show that one can obtain those solutions from solutions on the torus, via the twist transformation. The latter is then able to relate backgrounds which are not Tduals. Finally, we will apply this twist transformation technique to relate Kähler/nonKähler solutions of the heterotic string. This talk is based on a work with Enrico Goi, Ruben Minasian and Michela Petrini, 0903.0633 and to appear soon."  26Nov2009: Structure of gauge and gravity amplitudes in string and field theory
Pierre Vanhove (IHES, BuressurYvette and CEA/Saclay, GifsurYvette)
[Transparencies]
Abstract: "Recently, there have been remarkable progresses on the analysis of the multiloop amplitudes in supergravity in various dimensions using string theory and in field theory methods. There are strong indications that fourdimensional maximal supergravity theories have a better ultraviolet behaviour than expected from a conservative implementation of onshell superspace, and is a intricate consequence of gauge invariance and supersymmetry. As well the N=8 supergravity amplitudes have a much more simple structure than guessed from a traditional approach based on a Lagrangian and Feynman graphs formalism, and display striking similarities with N=4 superYangMills amplitudes. In this talk we will analyze the constraints from supersymmetry, gauge invariance on the ultraviolet behaviour of maximally supergravity gauge theories in various dimensions. We will compare the ultraviolet behaviour of N=4 superYangMills amplitudes at higherloop order in the leading and subleading color factor and compare with the expectations for N=8 supergravity amplitude in various dimensions."  03Dec2009: Probing strongly coupled gauge theories with AdS/CFT: The violation of the shear viscosity to entropy bound
Sera Cremonini (University of Cambridge)
[Transparencies]
Abstract: "The gauge gravity duality has proven to be a powerful tool for probing thermal and hydrodynamic properties of strongly coupled field theories, with possible applications to the realm of RHIC and QCDlike theories. In this talk I will discuss some of the recent applications of AdS/CFT to the ratio of the shear viscosity to entropy density. In particular, I will focus on the role played by higher derivative corrections at finite chemical potential. I will also touch on possible fundamental constraints that gravity might be imposing on the set of allowed dual CFTs, in the context of the weak gravity conjecture."  09Dec2009: Holographic flavor transport
Andrew O'Bannon (Max Planck Institute, Munich)
[Blackboard talk]
Abstract: "Gaugegravity duality is an extremely useful tool for studying stronglycoupled gauge theories, and has many applications to realworld systems, such as the quarkgluon plasma and quantum critical points. It is especially useful for studying the hydrodynamics of stronglycoupled nonAbelian gauge theories. For example, gaugegravity duality is currently the only reliable way to compute transport coefficients for many theories. In this talk I will describe a calculation of a transport coefficient, a conductivity, associated with flavor fields in a stronglycoupled plasma. From the result for the conductivity, I will show how gaugegravity duality captures a lot of realworld physics, such as momentum dissipation, Schwinger pair production, and more."
 15Jan2009: Black hole microstate geometries and the information paradox
 2008:
Lent 24Jan2008: Type II small stringy black holes, probe branes and higher derivative corrections
Linda UruchurtuGomez (University of Cambridge)  31Jan2008: Higher derivative corrections in IIB string theory on T^{2}
Anirban Basu (Institute for Advanced Study, Princeton)  07Feb2008: Nonperturbative superpotentials across lines of marginal stability
Inaki GarciaExtebarria (CERN)  14Feb2008: Supergravitons from oneloop perturbative N=4 SYM
Maciej Trzetrzelewski (University of Stockholm)  21Feb2008: Axion inflation in type II string theory
Thomas Grimm (University of Bonn and Wisconsin University, Madison)  28Feb2008: Twistor strings with flavour
James Bedford (Imperial College London)  06Mar2008: Finding vacua in string phenomenology
James Gray (University of Oxford)  13Mar2008: TBA
Benjamin Zwiebel (University of Cambridge)

Easter TBI

Michaelmas 09Oct2008: Stringy corrections to holographic hydrodynamics
Miguel Paulos (University of Cambridge)  16Oct2008: Generating stationary axisymmetric solutions of Einstein's vacuum equations in 5d and a black ring in TaubNUT
Pau Figueras (University of Durham)  23Oct2008: Compactification of higher derivative corrections and automorphic forms
Daniel Persson (Universite Libre de Bruxelles)  30Oct2008: ChernSimons quivers and SasakiEinstein manifolds
James Sparks (University of Oxford)  06Nov2008: Sigma model dualities and dual superconformal symmetry
Martin Wolf (University of Cambridge)  13Nov2008: The chiral ring of AdS_{3}/CFT_{2} and the attractor mechanism
Kyriakos Papadodimas (University of Amsterdam)  20Nov2008: Summing the instantons in the heterotic string
Jock McOrist (University of Chicago)  27Nov2008: Free fermions on quantum curves
Lotte Hollands (University of Amsterdam)  04Dec2008: External fields and the dynamics of flavours in holographic duals of large N gauge theories
Arnab Kundu (University of Southern California, Los Angeles)
 24Jan2008: Type II small stringy black holes, probe branes and higher derivative corrections
 2007:
Lent 18Jan2007: Moduli stabilisation and de sitter string vacua from magnetised D7 branes
Kerim Suruliz (University of Cambridge)  25Jan2007: Nongeometric flux compactifications
Brian Wecht (MIT, Boston)  01Feb2007: Holographic QCD and perfection
Nick Evans (University of Southampton)  08Feb2007: Cancelled
 15Feb2007: Aspects of nonAbelian 2d gauge theories and mirror symmetry
David Tong (University of Cambridge)  22Feb2007: Superparticles in AdS
Michael Chesterman (CEA, Saclay)  01Mar2007: A scattering phase for AdS_{5} x S^{5} strings
Rafael Hernandez (CERN)  08Mar2007: A magical mystery tour around some spots in the Landscape
Florian Gmeiner (NIKHEF, Amsterdam)  15Mar2007: Cancelled
 22Mar2007: TBA
Sean Hartnoll (KITP, Santa Barbara)

Easter 26Apr2007: Bubbling geometries from gauge theory
Diego Correa (University of Cambridge)  03May2007: Charges from attractors
Nemani Suryanarayana (Imperial College London)  10May2007: How many giants live near a black hole?
Aninda Sinha (University of Cambdridge)  17May2007: Connecting giant magnons to the ppwave: An Interpolating limit of AdS_{5} x S^{5}
Ian Swanson (Institute for Advanced Study, Princeton)  24May2007: AdS_{5} black holes and supersymmetry
James Lucietti (University of Durham)  31May2007: Dbrane instanton effects in IIA string vacua and their phenomenological implications
Timo Weigand (University of Pennsylvania)  07Jun2007: Breathing magnons
Keisuke Okamura (University of Tokyo)  14Jun2007: Marginal stability and dyon spectrum in N=4 supersymmetric string theories
Ashoke Sen (HarishChandra Research Institute, Allahabad)  21Jun2007: Rigid limit in N=2 supergravity and weakgravity conjecture
Yuji Tachikawa (Institute for Advanced Studies, Princeton)

Michaelmas 27Sep2007: Thermal derivation of the Colemande Luccia tunnellig prescription
Adam Brown (Columbia University, New York)  04Oct2007: TBA
YangHui He (University of Oxford)  11Oct2007: Backreacting flavours in the KlebanovStrassler Background: A new cascade
Francesco Benini (SISSA, Trieste)  18Oct2007: Supersymmetric AdS black holes
Harvey Reall (University of Cambridge)  25Oct2007: Polytopes and the landscape of hidden dimensions
Max Kreuzer (University of Vienna)  01Nov2007: This seminar is joint with the Isaac Newton Institute
Tristan McLoughlin (Penn State University)  08Nov2007: This seminar is joint with the Isaac Newton Institute
Kostas Skenderis (University of Amsterdam)  15Nov2007: TBA
 22Nov2007: Quantum corrections and the large volume scenario
Michael Haack (LudwigMaximilians University, Munich)  29Nov2007: TBA
 18Jan2007: Moduli stabilisation and de sitter string vacua from magnetised D7 branes