Joint seminars academic year: 2011-2012
Emergent Space Model Building and the Example of Ads_5XS^5
Frank Ferrari (ULB)
Wednesday, May 2, 2012 - 10:30
Leuven, Celestijnenlaan 200E 01.207
After an introduction to the concept of emergent space and its consequences for the theory of quantum gravity, we discuss a strategy to build calculable models of emergent space, based on the study of matrix effective actions for large $N$ vector models. Applying the idea to the type IIB background generated by $N$ D3 branes in the near horizon limit, we explain how the full ten dimensional space-time equipped with the correct AdS_5 x S^5 metric and self-dual Ramond-Ramond field strength emerge from a purely field theoretic calculation describing the microscopic interactions between k D-instaton probes and the N D3-branes in the large N limit. We briefly discuss some consequences and possible generalisations.
Gravity duals of supersymmetric gauge theories on curved manifolds
James Sparks (Oxford University)
Wednesday, April 25, 2012 - 13:00
Leuven, Celestijnenlaan 200E 01.207
It has recently been shown that one can define three-dimensional N=2 supersymmetric gauge theories on compact curved manifolds (certain squashed spheres and Lens spaces). Moreover, the expectation value of any BPS operator in such a theory localizes, reducing the path integral to a finite dimensional matrix integral. I will explain how to construct gravity duals to a large class of such theories, which have a large N limit. The gravitational free energy is shown to precisely match the corresponding field theory free energy, as a function of geometric parameters in the large N limit.
Non-standard Higgs decays and LHC signatures from low scale supersymmetry breaking
Christoffer Petersson (IFT, Madrid) .
Wednesday, April 25, 2012 - 10:30
Leuven, Celestijnenlaan 200E 01.207
In light of the recent Higgs and supersymmetry searches at the LHC, I will discuss how the spectrum and phenomenology of the MSSM Higgs sector is modified in scenarios where supersymmetry is broken spontaneously at around the TeV scale. In such scenarios, additional tree-level contributions to the quartic Higgs potential become relevant and a standard model-like Higgs particle with a mass of 125 GeV can easily be accommodated, without requiring large radiative corrections. Moreover, the Higgs particle can decay into a gravitino and a neutralino, which subsequently decays promptly into a photon and another gravitino, giving rise to final state consisting of a photon and missing transverse energy. I will estimate the relevant standard model backgrounds and present prospects for discovering this Higgs decay channel by the 2012 LHC run.
On the perturbative structure of scattering amplitudes of massless particles and the space of interacting theories.
Paolo Benincasa (Santiago de Compostela)
Wednesday, April 18, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 9th floor, Salle des Professeurs
In this talk we discuss the existence of a simple structure for tree level scattering amplitudes of massless particles. In particular, the generalisation of the BCFW-construction to include those theories whose amplitudes do not vanish as some momenta are taken to infinity allows us to point out the general existence of recursive structure, at least for theories with propagator 1/P^2. Equipped with such a generalised recursive relation and with consistency conditions at four-particle level, we are able to rediscover all the known theories characterised by three-particle couplings and propagator 1/P^2. This analysis seems to leave room for high-spin couplings, provided that at least the requirement of locality is weakened. We do not claim to have found tree-level consistent high-spin theories, but rather that our methods show signatures of them and possibly, with a suitable modification, they can be a good framework to perform a systematic search.
Banishing AdS ghosts with a UV cutoff
Tomás Andrade (UCSB, Santa Barbara)
Wednesday, April 18, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO, 9th floor, Salle des Professeurs
A recent attempt to make sense of scalars in AdS with "Neumann boundary conditions" outside of the usual BF-window $-(d/2)^2 < m^2 l^2 < -(d/2)^2 + 1$ led to pathologies including (depending on the precise context) either IR divergences or the appearance of ghosts. Here we argue that such ghosts may be banished by imposing a UV cutoff. It is also possible to achieve this goal in certain UV completions. An example is the above AdS theory with a radial cutoff supplemented by particular boundary conditions on the cutoff surface. In this case we explicitly identify a region of parameter space for which the theory is ghost free. At low energies, this theory may be interpreted as the standard dual CFT (defined with "Dirichlet" boundary conditions) interacting with an extra scalar via an irrelevant interaction.
Holographic Wilson loops and topological insulators
Andy O'Bannon (Cambridge)
Wednesday, March 28, 2012 - 13:00
Leuven, Celestijnenlaan 200E 01.207
Topological Insulators (TI's) are materials characterized by gapless edge states producing quantized, dissipationless transport. In more formal terms, they are defined as insulating materials characterized by a topological quantum number distinct from the vacuum. They thus fall outside the Landau-Ginzburg paradigm in which materials are classified by symmetry-breaking order parameters. Examples of TI's include quantum Hall systems, for which the topological quantum number is an integer (the quantized Hall conductivity), and recently-discovered materials for which the topological quantum number is Z2-valued. These systems all admit effective descriptions in terms of non-interacting electrons. Indeed, a complete classification now exists of all possible TI's described by non-interacting electrons. An open question is what kinds of TI states are possible in the presence of interactions. Gauge-gravity duality, or holography, gives us access to strongly-interacting systems, including some special TI's. In this talk I will describe one example a "holographic topological insulator," and compare the potential that a test charge feels in the presence of that TI, as computed from Wilson loops, to the result for real TI's.
Gauged supergravity and Borcherds algebras
Jakob Palmkvist
Wednesday, March 28, 2012 - 10:30
Leuven, Celestijnenlaan 200E 01.207
Gauge deformations of maximal supergravity in D=11-n dimensions generically give rise to a tensor hierarchy of p-form fields that transform in specific representations of the global symmetry group E(n). We derive the formulas defining the hierarchy from an extension of E(n) to a Borcherds superalgebra. This explains why the E(n) representations in the tensor hierarchies also appear in the level decomposition of the Borcherds superalgebra. We show that the indefinite Kac-Moody algebra E(11) can be used equivalently to determine these representations, and that this equivalence also holds for corresponding Borcherds and Kac-Moody extensions of arbitrary simple finite-dimensional Lie algebras. The talk is based on the papers 1110.4892 and 1203.5107.
The Resurgent Bootstrap and the 3D Ising Model
Sheer El-Showk (Saclay, Paris)
Wednesday, March 21, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
In recent years the conformal bootstrap has emerged as a surprisingly powerful tool to study CFTs in dimensions greater than two. In this talk I will explain how crossing symmetry of the four-point function of scalar operators can be used to extract very non-trivial constraints on the spectrum of a putative CFT in arbitrary spacetime dimension. Applying these techniques in 3D we will find that the 3D Ising model lies at a special point in the space of CFTs. Moreover, we will show that constraints from conformal invariance can be used to significantly reduce the error in the known estimates for the dimensions of operators and suggest a method to generalize this to a compute the dimensions of all operators in the theory. Time permitting I will mention some applications of this technology to holography and other CFT settings.
Holographic thermalization of entanglement entropy, mutual and tripartite information in 2d CFTs.
Federico Galli (VUB)
Wednesday, March 21, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
I will introduce the notions of entanglement entropy, mutual and tripartite information. I will then explain how these quantities can be computed holographically in strongly coupled 2d CFTs following a homogeneous deposition of energy, modeled as an infalling shell in AdS. A simple causality argument qualitatively explains our results for the thermalization of the entanglement entropy and of the mutual information.
Unitarity Constraints in Holography and Field theory
Manuela Kulaxizi (ULB)
Wednesday, March 14, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
We will review unitarity constraints on the central charges of four dimensional conformal field theories and also discuss how they can be made manifest in holography. It turns out, that Lovelock gravity is an excellent holographic toy model for this purpose. Holography then leads us to an alternative derivation of these constraints in conformal field theories. We discuss how to generalize this study to quantum field theories away from fixed points.
Three-sphere partition function, counterterms and supergravity
Cyril Closset (Weizmann Inst.)
Wednesday, March 14, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
The partition function of 3d N=2 superconformal theories on the 3-sphere can be computed exactly by localization methods. I will explain some sublteties associated to that important result. As a by-product, this analysis establishes the so-called F-maximization principle for N=2 SCFTs in 3d: the exact superconformal R-charge maximizes the 3-sphere free energy F=-log Z.
Anomalous Transport form Kubo Formulas
Karl Landsteiner (Madrid, IFT)
Wednesday, March 7, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
Chiral anomalies are some of the most fundamental properties of relativistic quantum field theories. At finite density and temperature they give rise to new dissipationless transport phenomena. These are of direct relevance to heavy ion collisions and induce the so called Chiral Magnetic Effect. I will show how the anomalous transport coefficients, the chiral magnetic and the chiral vortical conductivity can be studied via Kubo formulas at weak and strong coupling.
RR Photons
Fernando Marchesano (Madrid, IFT)
Wednesday, March 7, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO 5th floor, Salle Solvay
We will survey several aspects of Type II string phenomenology, and in particular of the gauge group that one obtains upon compactifications to 4d. While the Standard Model gauge group generically arises from D-branes, there are additional U(1) symmetries that arise from the Ramond-Ramond sector of the theory. As there is no massless matter charged under the latter, it is a priori difficult to measure any physical consequences of their existence. There is however a window of opportunity if these RR U(1)’s mix with the hypercharge. We will discuss different avenues by which RR U(1)'s may mix with D-brane U(1)’s, and provide geometric criteria for the existence of such mixing. A particularly interesting case is when U(1)'s mix via the mass terms induced by Stuckelberg couplings, that happens whenever D-branes wrap torsional p-cycles in the compactification manifold. We will show that such mass mixing may induce corrections relevant for hypercharge gauge coupling unification in F-theory GUT models.
Dynamical Completions of Generalized O'Raifeartaigh Models
Lorenzo Di Pietro
Wednesday, February 29, 2012 - 13:00
Leuven, Celestijnenlaan 200E 01.207 (map)
We start reviewing the interplay between Dynamical Supersymmetry Breaking and R-symmetry, and the related problem of gaugino screening. We discuss the features of the low energy O'Raifeartaigh models that can give unsupressed gaugino mass. Based on 1111.2307 we present gauge theory completions of such models, admitting supersymmetry breaking vacua with spontaneously broken R-symmetry. Our models are simple deformations of generalized ITIY models, a supersymmetric theory with gauge group Sp(N), N+1 flavors plus singlets, with a modified tree level superpotential which explicitly breaks (part of) the global symmetry. Depending on the nature of the deformation, we obtain effective O'Raifeartaigh-like models whose pseudomoduli space is locally stable in a neighborhood of the origin of field space, or in a region not including it. Hence, once embedded in direct gauge mediation scenarios, our models can give low energy spectra with either suppressed or unsuppressed gaugino mass.
Conical spaces in higher spin gravity
Joris Raeymaekers (ASCR, Czech Republic)
Wednesday, February 29, 2012 - 10:30
Leuven, Celestijnenlaan 200E 01.207
In 2+1 dimensions, AdS gravity coupled to higher spins has an elegant description as an SL(N) Chern-Simons gauge theory. I will consider conical defect solutions in this theory and argue that (for N ≥ 4) there are special values of the deficit angle for which these geometries are actually smooth configurations of the gauge theory. I will also comment on the role of these configurations in the proposed holographic duality with W_N minimal model CFTs. In particular, I will argue that the spectrum of smooth SL(N, C) solutions matches exactly with that of the so-called "light primaries" in the minimal model W_N CFTs at finite N, in a suitable classical limit.
Higher-Spin Interactions: on four-point functions and beyond
Massimo Taronna (Pisa)
Wednesday, February 22, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
Recasting the Noether procedure in terms of generating functions, I will present its most general solution obtaining handy expressions for bosonic higher-spin Noether currents whose form was first recovered from the tensionless limit of String Theory. I shall also describe a class of higher-spin four-point functions and the corresponding Lagrangian couplings pointing out their intrinsic non-local nature. The construction clarifies the origin of old problems for these systems and links String Theory to some aspects of Field Theory that go beyond its conventional low energy limit.
Holography of the tachyon
Andrei Parnachev (Leiden)
Wednesday, February 22, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
I will present a holographic model which describes field theories with dynamically generated mass in terms of the tachyon DBI action in AdS spacetime. The model is motivated by the D-brane constructions in string theory. Possible applications include conformal phase transitions in QCD-like theories, walking technicolor models and strongly interacting matter at finite temperature.
Transverse invariant Lagrangians for higher spins
Andrea Campoleoni (MPI Golm)
Wednesday, February 15, 2012 - 13:00
VUB/ULB, Campus Plaine, building NO, 9th floor, Salle des Professeurs
I will show how implementing invariance under transverse-free gauge transformations leads to a remarkably simple Lagrangian description of massless bosons of any spin. Actions of this type can be defined on both flat and (A)dS backgrounds and they can be built also for tensors of arbitrary mixed-symmetry type.
Anisotropic Lattice Gauge Theories with Extra Dimensions
Stam Nicolis
Wednesday, February 15, 2012 - 10:30
VVUB/ULB, Campus Plaine, building NO, 9th floor, Rm 906, Salle des Professeurs
We study lattice gauge theories with compact gauge group in terms of variables that explicitly solve the constraints. We show how the anisotropy can lead to a second order phase transition, where the gauge fields are localized on submanifolds. This effect arises for strong gauge coupling along the extra dimensions and can be interpreted as an example of flux compactification. We also demonstrate the equivalence between theories with U(1) and SU(2) gauge groups, within the mean field approximation and when taking certain corrections into account. Chiral fermions can be included in a very interesting way.
AdS black holes in supergravity
David Chow (ULB)
Wednesday, February 1, 2012 - 13:00
Leuven, Celestijnenlaan 200N 00.01
The 4-dimensional Kerr black hole plays a central role in understanding many aspects of gravity. It has since been generalized, in particular to asymptotically AdS, charged, rotating black holes of maximal gauged supergravities in various dimensions. I shall give an overview of these solutions, explaining the ideas behind their construction, and some of their uses.
Black hole instabilities and local Penrose inequalities
Harvey Reall (Cambridge)
Wednesday, February 1, 2012 - 10:30
Leuven, Celestijnenlaan 200N 00.01
Various higher-dimensional black holes have been shown to be unstable by studying linearized gravitational perturbations. This is often very complicated. I shall describe a simpler method for demonstrating instability. The idea is to construct initial data describing a small perturbation of the black hole and which violates an inequality analogous to the 4d Penrose inequality.
Constraining theories with higher spin symmetry
Juan Maldacena (IAS)
Tuesday, January 17, 2012 - 10:30
VUB/ULB, Campus Plaine, building NO 5th floor, Salle Solvay
We consider conformal field theories with exactly conserved currents of spin s > 2. We show that such theories are essentially free theories. This is an extension of the Coleman Mandula theorem to the case of conformal field theories. We also discuss the case where the higher spin symmetry is slightly broken. This is based on papers by JM and A. Zhiboedov, *arXiv:1112.1016 & to
Observing holographic superconductivity in the laboratory.
Jan Zaanen (Leiden)
Wednesday, December 14, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
The promise of the present flirtation between string theory and condensed matter physics is that the former will finally demonstrate empirical relevance by shedding light on the great mysteries of the latter. The holy grail problem in condensed matter has been since 25 years the mechanism of superconductivity at a high temperature. On the other hand, the first substantial result produced by the AdS/CFT correspondence in this context is the discovery of holographic superconductivity by Gubser and Hartnoll-Herzog-Horowitz in 2008. This demonstrates that the superradiance instability of an AdS Reissner-Nordstrom black hole in the presence of a scalar field dualizes in the statement that a strongly interacting conformal field theory at a finite density has a superconducting instability that bears similarities to the standard BCS mechanism while it is yet very different. I will present and explain the design of an experiment that is practical enough to be realized in the experimental laboratory, being taylored to observe the qualitative differences between the BCS and the holographic mechanisms [1]. [1] J.-H. She et al., Phys. Rev. B 84, 144257 (2011); D. van der Marel and J.N. Hancok, Physics 4, 89.
Momentum space entanglement and renormalization in quantum field theory
Vijay Balasubramanian (University of Pennsylvania)
Wednesday, December 14, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
The degrees of freedom of any interacting quantum field theory are entangled in momentum space. Thus, in the vacuum state, the infrared degrees of freedom are described by a density matrix with an entanglement entropy. We derive a relation between this density matrix and the conventional Wilsonian effective action. We argue that the entanglement entropy of and mutual information between subsets of field theoretic degrees of freedom at different momentum scales are natural observables in quantum field theory and demonstrate how to compute these in perturbation theory. The results may be understood heuristically based on the scale-dependence of the coupling strength and number of degrees of freedom. We measure the rate at which entanglement between degrees of freedom declines as their scales separate and suggest that this decay is related to the property of decoupling in quantum field theory
Trivertices and SU(2)'s
Amihay Hanany (Imperial College London)
Wednesday, December 7, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
Given a graph with lines and 3-valent vertices, one can construct, using a simple dictionary, a Lagrangian that has N=2 supersymmetry in 3+1 dimensions. This is a construction which generalizes the notion of a quiver. The vacuum moduli space of such a theory is well known to give moment map (F & D term) equations for a HyperKahler manifold. We will discuss the class of hyperkahler manifolds which arise due to such a construction and present their special properties. The Hilbert Series of these spaces can be computed and turns out to be a function of the number of external legs and loops in the graph but not on its detailed structure. The corresponding SCFT consequence of this property indicates a crucial universality of many Lagrangians, all of which have the same dynamics. The talk is based on http://arXiv.org/pdf/1012.2119
Unbalanced Holographic Superconductors and Spintronics
Francesco Bigazzi (University of Florence and INFN)
Wednesday, December 7, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
Superconductivity driven by the condensation of two fermionic species with different chemical potential is an interesting possibility relevant both in condensed matter and in finite density QCD setups. The imbalance of spin populations in ferromagnetic materials is also a relevant ingredient of spintronics, the branch of electronics concerned with the study and applications of spin transport. While the behavior of unbalanced setups is well established at weak coupling, a precise theoretical model describing their physics in strongly-coupled unconventional systems (e.g. in quantum critical regions) is still lacking. With the aim of providing some toy-model-based insights on this issue, I will present the simplest holographic realization of strongly coupled unbalanced s-wave superconductors and forced ferromagnets in 2+1 dimensions. I will describe both equilibrium (phase diagram) and transport properties of these systems, with a focus on the conductivity matrix for charge, spin and heat currents.
A ten-dimensional action for non-geometric fluxes
Magdalena Larfors (LMU, Munich)
Wednesday, November 30, 2011 - 13:00
Leuven, Celestijnenlaan 200D room 05.11
In ten- and four-dimensional supergravities, the descriptions of non-geometric configurations are different. In the former, non-geometry arises as naively non-single valued supergravity fields. In the latter, new terms, coming from non-geometric Q- and R-fluxes, appear in the four-dimensional potential. In this talk, it is shown that a ten-dimensional field redefinition results in a Q-flux term in the NSNS Lagrangian. This change of field basis is inspired by generalized complex geometry. We argue that this new field basis provides a good description of certain non-geometric configurations. In particular, using the new basis, a dimensional reduction can be performed, in which the Q-flux term gives rise to the expected term in the four-dimensional potential. We also discuss the global issues of this set-up.
T-duality for massive stringy states: A world sheet perspective
Jnanadeva Maharana (Bhubaneswar, India)
Wednesday, November 30, 2011 - 10:30
Leuven, Celestijnenlaan 200D room 05.11
We provide evidence for T-duality, from the worldsheet perspective, for massive excited levels of closed bosonic string. A simple scenario is envisaged where the target space is flat. In this frame work, it is argued that the vertex operators associated with the massive levels can be cast in an O(d,d) invariant form where d is the number of compact directions and the vertex operators are assumed to be independent of compact coordinates.
Holographic no-boundary measure
Thomas Hertog (K.U.Leuven)
Wednesday, November 23, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
We show that the complex saddle points of the no-boundary wave function with a positive cosmological constant and a positive scalar potential have a representation in which the geometry consists of a regular Euclidean AdS domain wall that makes a smooth transition to a Lorentzian, inflationary universe that is asymptotically de Sitter. This leads to a dual formulation of the semiclassical no-boundary wave function - and thus a concrete realization of a dS/CFT duality - in terms of field theories on the final boundary that are certain relevant deformations of the CFTs that occur in AdS/CFT. The implications of this for the no-boundary measure in eternal inflation will be briefly discussed.
Dimensional reductions of Double Field Theory
Diego Marqués (CEA Saclay)
Wednesday, November 23, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
The talk begins with a brief review of Double Field Theory (DFT), its field content, symmetries and action. I will then analyze generalities of Scherk-Schwarz dimensional reductions of DFT. In particular, the connection between the effective actions and gauged supergravities will be discussed. The talk is mostly based on "The effective action of Double Field Theory", arXiv:1109.0290 [hep-th].
M5's, D4's, 5D SYM and instantons
Neil Lambert (CERN Theory Division)
Wednesday, November 16, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
We will discuss the M5-brane and its relation to D4-branes. An important role is played by instantons and we conjecture that 5D SYM is an interesting QFT that is possibly finite.
Higher-spin theories in odd dimensions
Shailesh Lal (Harish-Chandra Research Institute)
Wednesday, November 16, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
We describe aspects of higher-spin theories in odd (specifically 3 and 5) dimensions. We first discuss the deformation of D=3 higher-spin theories by a topological mass term and provide evidence that the dual CFT is logarithmic. We then go on to compute the one-loop partition function of the higher-spin fields in AdS_5 and compare with the boundary spectrum. Central to these results are the heat kernel expressions for arbitrary-spin particles in AdS, which we shall review.
M-theory and generalised geometry
David Berman (Queen Mary)
Wednesday, November 9, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
We give an overview of recent developments in using generalised geometry to constract duality symmetric actions in M-theory.
Thermalization and entanglement following a non-relativistic holographic quench
Esko Keski-Vakkuri (Helsinki University)
Wednesday, November 9, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 5th floor, Salle Solvay
Recently it has become possible to construct toy models for thermalization from a far-from-equilibrium initial state in a strongly coupled relativistic quantum field theory. These toy models are based on the so-called holographic duality, where a quantum field theory is somewhat miraculously rewritted as a gravitational theory in one higher dimension. In my talk I discuss one way to modify these constructions to non-relativistic non-equilibrium dynamics.
Supergravity as Generalised Geometry
Daniel Waldram (Imperial College, London)
Wednesday, October 26, 2011 - 13:00
Leuven, Celestijnenlaan 200D room 05.11
We argue that generalised geometry with O(d,d) and Ed(d) structure groups gives a natural framework for formulating type II and eleven-dimensional supergravity theories, as generalisations of conventional Riemannian geometry. The bosonic symmetries are unified and the bosonic fields define a substructure in analogy to a conventional metric. We introduce the analogues of the Levi-Civita connection and Ricci curvature and show that these structures allow one to rewrite the action, equations of motion and supersymmetry variations in a simple form with an enhanced local symmetry. Locally this formalism is equally applicable to so-called "doubled field theories" and we note interesting connections to the embedding tensor formalism.
Global Aspects of F-theory GUTs
Sakura Schäfer-Nameki (King's College London)
Wednesday, October 26, 2011 - 10:30
Leuven, Celestijnenlaan 200D room 05.11
I will give an overview of recent developments in understanding global aspects of F-theory compactifications that are relevant for realizing supersymmetric GUTs, including the more formal aspects of resolution of singular CY fourfolds and construction of G-fluxes.
Holographic Correlators of Giant Gravitons
Konstantinos Zoubos (Niels Bohr Institute, Copenhagen)
Wednesday, October 12, 2011 - 13:00
VUB/ULB, Campus Plaine, building NO, 9th floor, Salle des Professeurs
The appearance of integrability in N=4 SYM has provided an unprecedented level of information about the planar spectrum of the theory. Recently, some attention has shifted from the spectrum to three-point functions of operators with large quantum numbers, aiming to ascertain whether integrability plays a similarly important role for these observables. I will discuss the computation, on both sides of the AdS/CFT correspondence, of three-point functions involving two "heavy" operators dual to giant gravitons and one "light" single-trace chiral primary, and point out an intriguing puzzle that arises when comparing the gravity and gauge theory results.
Mellin amplitudes in AdS/CFT
Miguel Paulos (LPTHE, Paris)
Wednesday, October 12, 2011 - 10:30
VUB/ULB, Campus Plaine, building NO, 9th floor, Salle des Professeurs
Thermodynamics and instabilities of a strongly coupled anisotropic plasma
David Mateos (Barcelona)
Wednesday, October 5, 2011 - 13:00
Leuven, Celestijnenlaan 200D room 05.11
I will present a IIB supergravity solution dual to a spatially anisotropic finite-temperature N=4 super Yang-Mills plasma. I will discuss its thermodynamics and show that the phase diagram exhibits homogeneous and inhomogeneous (i.e. mixed) phases. In some regions the homogeneous phase displays instabilities reminiscent of those of weakly coupled plasmas. I will comment on similarities with QCD at finite baryon density and with the phenomenon of cavitation.
Curved Superspace
Nathan Saiberg (IAS, Princeton)
Wednesday, October 5, 2011 - 10:30
Leuven, Celestijnenlaan 200D, Room 05.11
A certain limit of supergravity “the rigid limit” leads us to a unified and efficient description of supersymmetric field theories in rigid curved spacetime. We will present the general formalism and will demonstrate it in a few examples. We will also summarize some of the new insights about the dynamics that such theories in curved spaces teach to.