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Workshop Programme

for period 28 May - 1 June 2012

Branes and Black Holes (A London Satellite Meeting)

28 May - 1 June 2012

Timetable

Monday 28 May
09:30-10:15 Registration
10:15-11:00 Denef, F (Katholieke Universiteit Leuven)
  String glasses and beyond
 

I will review some recent work on complex, glassy systems in string theory and cosmology.

 
11:00-11:30 Morning Coffee - Great Hall Foyer
11:30-12:15 Bena, I (Institut de Physique Theorique, CEA Saclay)
  Microstate Geometries - what do they tell us about Black Holes?
 

Black hole microstate geometries exist in the same regime of parameters as a large classical black hole, but have no horizon. One can construct incredibly-large families of such geometries, and argue that they have the right properties to describe some of the typical microstates of the black hole. I will review the construction and properties of microstate solutions for supersymmetric, extremal non-supersymmetric and nonextremal black holes, and discuss what they teach us about black hole physics.

 
12:15-13:00 Skenderis, K (Universiteit van Amsterdam)
  Lifshitz as a deformation of AdS
13:00-14:00 Lunch - Terrace
14:00-14:45 Murthy, S (Universiteit Utrecht)
  Some progress in computing exact black hole entropy using localization
 

I will report on some recent progress in computing the exact quantum entropy of supersymmetric black holes using localization techniques. After a brief review of recent developments, I will present new results on the derivation of the full solution manifold of the localization equations in N=2 supergravity. I will then discuss some clues that are emerging about the (ir)relevance of (non) F-terms to the quantum black hole entropy.

 
14:45-15:30 Manschot, J (Universität Bonn)
  D-branes on elliptic Calabi-Yau manifolds
 

I'll discuss the quantum geometry of elliptically fibered Calabi-Yau threefolds. A holomorphic anomaly equation for the topological string free energy is proposed, which is iterative in the genus expansion as well as in the curve classes in the base. T-duality on the fibre implies that the topological string free energy also captures the BPS-invariants of D4-branes wrapping the elliptic fibre and a class in the base. We verify this proposal by explicit computation of the BPS invariants of 3 D4-branes on the rational elliptic surface.

 
15:30-16:00 Afternoon Tea - Great Hall Foyer
16:00-16:45 Ross, S (University of Durham)
  Holography for asymptotically locally Lifshitz spacetimes
 

I will review the holographic description of field theories with an anisotropic scaling symmetry. I will explain how to define general boundary data for this correspondence, and discuss the asymptotic expansion (the analogue of the Fefferman-Graham expansion) and the holographic renormalization for general boundary data. At the end of the talk, I will describe work in progress on alternative boundary conditions.

 
16:45-17:30 Guica, M (Université Pierre et Marie Curie)
  Un-twisting the NHEK with spectral flows
 

Schroedinger spacetimes geometrically realize the nonrelativistic conformal group, reason for which they have been proposed as holographic duals to strongly coupled non-relativistic CFTs. On the other hand, it has been recently shown that black holes in three-dimensional Schroedinger spacetimes exhibit a previously unknown Virasoro asymptotic symmetry, which is indicative of a full conformal symmetry. To uncover it, I will construct a Fefferman-Graham-like expansion for the relevant modes in asymptotically three-dimensional Schroedinger spacetimes by mapping them to an auxiliary AdS(3) spacetime, and show that the renormalized on-shell action for these modes is identical to the one for the gravity modes in the auxiliary AdS(3). The holographic stress-energy tensor one obtains by this procedure is symmetric, conserved and its trace yields the same conformal anomaly as in AdS(3).

 
18:00-19:00 Reception - Terrace
Tuesday 29 May
09:30-10:15 Trivedi, S (Tata Institute of Fundamental Research)
  Bianchi Attractors: A Classification of Extremal Black Brane Geometries
 

Extremal black branes are of interest because they correspond to the ground states of field theories at finite charge density in gauge/gravity duality. The geometry of such a brane need not be translationally invariant in the spatial directions along which it extends. A less restrictive requirement is that of homogeneity, which still allows points along the spatial directions to be related to each other by symmetries. In the talk we will discuss new classes of homogeneous but anisotropic extremal black brane horizons, which could naturally arise in gauge/gravity dual pairs. In 4+1 dimensional spacetime, we will show that such homogeneous black brane solutions are classified by the Bianchi classification, which is well known in the study of cosmology, and fall into nine classes.

 
10:15-11:00 Castro, A (McGill University)
  Black hole monodromy
 

In this talk we will revisit the computation of greybody factors using a novel set of tools based on the monodromy technique. Our aim is to emphasize that the analytic properties of the black hole background play a crucial role in the scattering problem. In particular, acknowledging the existence of the inner horizon allows for exact expressions of the transmission and reflection coefficients without taking any low or high frequency approximation. More interestingly, this approach sheds light on the CFT interpretation of the B-H entropy as a Cardy formula for a large class of black holes in 4D and 5D.

 
11:00-11:30 Morning Coffee - Great Hall Foyer
11:30-12:15 Martelli, D (King's College London)
  Supersymmetric field theories on curved manifolds and holography
 

I will discuss certain aspects of supersymmetric gauge theories on curved manifolds and how these interplay with holography in supersymmetric asympotically locally AdS geometries. In particular, I will present proposals for gravity duals of field theories on different squashed three-spheres.

 
12:15-13:00 Hartong, J (University of Copenhagen)
  Lifshitz Holographic Renormalization from AdS
 

Lifshitz space-times with critical exponent z=2 can obtained by dimensional reduction of Schroedinger space-times with critical exponent z=0. The latter space-times are asymptotically AdS solutions of AdS gravity coupled to an axion-dilaton system (or even just a massless scalar field). This basic observation is used to perform holographic renormalization for 4-dimensional asymptotically locally Lifshitz space-times by dimensional reduction of the corresponding problem of holographic renormalization for 5-dimensional asymptotically AdS space-times coupled to an axion-dilaton system. In this setup the 4-dimensional structure of the Lifshitz Fefferman-Graham expansion and the structure of the counterterm action, including the scale anomaly, will be discussed.

 
13:00-14:00 Lunch - Terrace
14:00-14:45 Takayanagi, T (Yukawa Institute for Theoretical Physics)
  Holographic Dual of BCFT
 

We propose a holographic dual of a conformal field theory defined on a manifold with boundaries, i.e. boundary conformal field theory (BCFT). This new holography successfully calculates the boundary entropy or g-function in two dimensional BCFTs and it agrees with the finite part of the holographic entanglement entropy. Moreover, we can naturally derive a holographic g-theorem. We conjecture a higher dimensional analogue of g-theorem and give some evidences from both the gravity and field theory side. We also discuss the gravity dual with boundaries with arbitrary shape.

 
14:45-15:30 El-Showk, S (CEA/Saclay)
  The Resurgent Bootstrap and the 3D Ising Model
 

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 D=3 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 more general applications of this technology, including holography.

 
15:30-15:45 Afternoon Tea - Great Hall Foyer
15:45-16:30 Bossard, G (Centre de Physique Théorique de l'Ecoe Polytechnique (CPHT))
  Octonionic black holes
 

I will display the generalisation of solutions describing bound states of interacting non-BPS extremal black holes to N=8 supergravity. I will explain in particular how gravitini N=2 multiplets vector fields and some hyper-multiplets scalars are involved in a non-trivial manner in these solutions. For this purpose I will define `special coordinates' for the N=8 moduli which generalise naturally the special Kaehler coordinates. Then I will display some physical properties of these solutions, and in particular the existence of three by three interactions that are absent in the BPS solutions, and which are responsible for an extra contribution to the ADM angular momentum.

 
16:30-17:15 Bianchi, M (Università degli Studi di Roma Tor Vergata)
  Massive and higher spin string scattering off D-brane bound-states
 

We study scattering amplitudes of higher spin closed-string states off D-brane bound-states. For states in the first Regge trajectory we find remarkable simplifications both at tree level and at one loop. We discuss the high energy behavior in the Regge limit and comment on the validity of the eikonal approximation in this regime.

 
18:00-21:00 Banquet - Quaglino's
Wednesday 30 May
09:30-10:15 Strominger, A (Harvard University)
  Progress in dS/CFT
10:15-11:00 Dall'agata, G (Università degli Studi di Padova)
  Flow equations for Black Holes in (gauged) supergravity
 

We review the fake superpotential formalism for describing extremal black holes and discuss its possible extensions to the case of black holes in asymptotically AdS spacetimes.

 
11:00-11:30 Morning Coffee - Terrace
11:30-12:15 Chowdhury, B (Universiteit van Amsterdam)
  Black holes spitting out supertubes
 

We search for stable bound states of non-extremal rotating three-charge black holes in five dimensions (Cvetic-Youm black holes) and supertubes. We do this by studying the potential of supertube probes in the non-extremal black hole background and find that generically the marginally bound state of the supersymmetric limit becomes metastable and disappears with non-extremality (higher temperature). However near extremality there is a range of parameters allowing for stable bound states, which have lower energy than the supertube-black hole merger. Angular momentum is crucial for this effect. We use this setup in the D1-D5 decoupling limit to map a thermodynamic instability of the CFT (a new phase which is entropically dominant over the black hole phase) to a tunneling instability of the black hole towards the supertube-black hole bound state. This generalizes the results of "Moulting Black Holes", which mapped an entropy enigma in the bulk to the dual CFT in a supersymmetric setup.

 
12:15-13:00 Cassani, D (King's College, London)
  Systematics of supersymmetric flows along the conifold
 

Working in N=4 gauged supergravity, we analyze the conditions for five-dimensional supersymmetric domain walls, which correspond to holographic RG flows. Applying our results to a class of consistent truncations of string theory, we obtain a general flow for SCFT deformations, as well as a new flow closely related to the resolved conifold. We also discuss a superpotential for the baryonic branch of the Klebanov-Strassler solution.

 
13:00-13:45 de Boer, J (Universiteit van Amsterdam)
  Some thoughts on black hole microstates
13:45-18:00 Free afternoon
Thursday 31 May
09:30-10:15 de Wit, B (Universiteit Utrecht)
  Deformations of special geometry; in search of the topological string
 

The possible relation between the effective action for N=2 supergravity with couplings proportional to the square of the Weyl tensor and the topological string partition function is explored. A number of systematic features is extracted with particular attention to the presence of non-holomorphic corrections.

 
10:15-11:00 Papadopoulos, G (King's College London)
  Brane and black hole supergravity horizons
 

Insights into the physics of gauge theories and strings have been gained by looking into the properties of the horizons of brane and black hole supergravity solutions. In this talk, I shall present a systematic exploration of the topology and geometry of such horizons utilizing the recent progress that has been made in the classification of supergravity backgrounds. The focus will be in heterotic, type II and M-horizons.

 
11:00-11:30 Morning Coffee - Great Hall Foyer
11:30-12:15 Larsen, F (University of Michigan)
  Conformal Symmetry for General Black Holes
 

The boundary conditions of general black holes in asymptotically flat spacetimes can be modified such that a conformal symmetry emerges. The black holes with asymptotic geometry modified in this manner satisfy the equations of motion of minimal supergravity in one dimension more. Their symmetry suggests that a dual conformal field theory description exists that can account for the black hole entropy even in the case of black holes that are far from extremality.

 
12:15-13:00 Virmani, A (Max-Planck-Institut fur Gravitationphysik)
  Subtracted Geometry From Harrison Transformations
 

We consider general four dimensional black holes in string theory and show that their subtracted geometry - which makes the hidden conformal symmetry manifest - can be obtained by applying Harrison transformations on the black holes.

 
13:00-14:00 Lunch - Great Hall Foyer
14:00-14:45 Ortin, T (Universidad Autonoma de Madrid)
  Constructing generic non-extremal black-hole solutions of N=2, d=4,5 supergravities
 

I will review the general construction of non-extremal black-hole and black-brane solutions of N=2,d=4 and d=5 supergravity coupled to vector multiplets, and their properties. I will describe the explicit solutions of a few models, their extremal (supersymmetric and non-supersymmetric) limits, entropies, non-extremality functions etc. and a formalism that simplifies dramatically the search and construction of those solutions.

 
14:45-15:30 Bagchi, A (University of Edinburgh)
  Flat Space Holography as a limit of AdS/CFT
 

We construct flat-space holography as a limit of usual AdS/CFT concentrating on the 3d bulk/2d boundary example. The asymptotic group of symmetries at null infinity of flat spacetimes is the infinite dimensional Bondi-Metzner-Sachs (BMS) group. We show how this emerges in the flat-space limit of AdS symmetries. The flat limit also induces a contraction on the CFT which in 2d reduces to the Galilean Conformal Algebra (GCA), studied previously in the context of non-relativistic systems. Quantum gravity in flat space would be described by the representations of the GCA. We comment on the relevant representations of the GCA and correlation functions. We also mention some intriguing results in ongoing work on the "flat" BTZ.

 
15:30-16:00 Afternoon Tea - Terrace
16:00-16:45 Rodriguez, M (Harvard University)
  Universal properties and the first law of black hole inner mechanics
 

Recently, we showed by explicit computations that the product of all the horizon areas is independent of the mass, regardless of the topology of the horizons. The universal character of this relation holds for all known five dimensional asymptotically flat black rings, and for black strings. This gives further evidence for the crucial role that the thermodynamic properties at each horizon play in understanding the entropy at the microscopic level. To this end we proposed a 'first law' for the inner Cauchy horizons of black holes. The validity of this formula, which seems to be universal, was explicitly checked in all cases.

 
16:45-17:30 Ramgoolam, S (Queen Mary, University of London)
  Branes, permutations and oscillators
 

The group theory of permutations plays a central role in understanding the emergence of giant graviton branes from gauge-invariant operators in the dual gauge theory. This holds for BPS operators as well as their non-BPS excitations. Young diagrams, Schur-Weyl duality and double cosets are some of the concepts that are useful in analysing the action of the gauge-theory one-loop dilatation operator acting on brane excitations. The analysis leads to harmonic oscillator systems describing strings attached to the branes. The talk will be based primarily on http://arxiv.org/abs/1204.2153.

 
Friday 1 June
09:30-10:15 Emparan, R (Universitat de Barcelona)
  Black brane fluid flows
 

We study how the hydrodynamics of a black brane changes when we enclose it in a finite cylindrical cavity with Dirichlet boundary conditions. For neutral black branes, we see how the Gregory-Laflamme instability switches off and study the critical point where the instability disappears. For black D3 branes, as the cavity radius decreases one obtains the sequence of descriptions "blackfolds > fluid/AdS-gravity > membrane paradigm". We show that, to leading order above extremality, "sound comes from the throat".

 
10:15-11:00 Song, W (Harvard University)
  Comments on dipole theories
 

Dipole theories are interesting for many reasons. On the one hand, the background is deformed, and therefore is a simple example of non-AdS holography. On the other hand, the bulk spacetime can be obtained by a generalized spectra flow, and therefore many properties are inherited from AdS. Furthermore, dipole/CFT duality is closely related to Kerr/CFT correspondence. By studying dipole theory, we could learn some information about the CFT that is dual to Kerr. In this talk I will comment on dipole/CFT duality, and string sigma models on dipole backgrounds.

 
11:00-11:30 Morning Coffee - Terrace
11:30-12:15 Giddings, S (University of California, Santa Barbara)
  Black holes, Hilbert-space networks, and quantum information transfer
 

A unitary resolution of the black hole information problem, or unitarity crisis, appears to require transfer of quantum information from black holes to their surroundings, in conflict with field-theory locality. One can both model and constrain such evolution. A possible general setting for such evolution, capturing some aspects of locality, is in a Hilbert-space network.

 
12:15-13:00 Reall, H (University of Cambridge)
  Black hole instabilities and local Penrose inequalities
 

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. I will describe recent work applying the method to non-uniform black strings.

 
13:00-14:00 Special lunch - Terrace

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