## Directions

Imperial College has its own detailed information on general directions and on getting to the theoretical physics group. The College is located on Prince Consort Road, south of Hyde Park (map). The most convenient access is via tube (South Kensington, Gloucester Road) or buses. The Theoretical Physics group resides on the 5th floor of the Huxley Building. The group also possesses its own description.

## Seminars at Imperial College

Found at least 20 result(s)

### 22.10.2015 (Thursday)

#### T-Self Duality of AdS(d) x S(d) x S(d) Superstrings

Exceptional Seminar Antonio Pittelli (Surrey University)

 at: 13:30 ICroom H503 abstract: Dual superconformal symmetry is a remarkable, hidden feature of N=4 SYM in 4 dimensions. Via AdS/CFT, such a symmetry corresponds to the invariance of the AdS(5) x S(5) superstring under specific combinations of bosonic and fermionic T-dualities. We show that AdS(d) x S(d) x S(d) superstrings with D(2,1;\alpha) isometry supergroup are T-self-dual if additional T-dualities along complexified S(d) directions are performed. This implies that CFTs dual to AdS(d) x S(d) x S(d) x T(10-3d) superstrings enjoy a new type of dual superconformal symmetry.

### 15.10.2015 (Thursday)

#### Interactions in Vasiliev's Theory, Holography and Locality

Exceptional Seminar Massimo Taronna (AEI)

 at: 13:30 ICroom H503 abstract: The aim of this talk is to extract the quadratic corrections to Fronsdal equations from Vasiliev's equations, and discuss their structure. The issue of locality in higher-spin theories will be addressed. Implications of this analysis in relation to Giombi-Yin checks of higher-spin/vector model duality will be discussed. Some of the previous puzzles will be resolved, while others will be elucidated.

### 14.10.2015 (Wednesday)

#### All order alpha' corrections to BPS,non-BPS and brane anti-brane effective actions of type IIA,IIB superstring theory

Regular Seminar Ehsan Hatefi (Queen Mary)

 at: 14:00 ICroom H503 abstract: We would like to talk about all kinds of supersymmetric and non-supersymmetric scattering amplitudes of type IIA,IIB superstring theory as well as their corrections. In fact we want to address how to get to a universal conjecture for DBI, Chern-Simons and more importantly new Wess Zumino actions with their all order $\alpha'$ corrections. Indeed we try to provide a comprehensive explanation even for D- brane-anti D-brane systems, where various new techniques will be also introduced. If time allows , we then mention several issues related to those effective actions and eventually highlight some comments about higher point functions of the Mixed closed string RR , scalar fields in different pictures of the string theory amplitude.

### 08.10.2015 (Thursday)

#### All gaugings and stable de Sitter in D=7 half-maximal supergravity

Regular Seminar Jose Fernandez-Melgarejo (Harvard)

 at: 13:30 ICroom H503 abstract: We study the general formulation of gauged supergravity in seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry.

### 29.07.2015 (Wednesday)

#### Connections on Courant Algebroids

Regular Seminar Branislav Jurco (Charles University/MPIM)

 at: 14:00 ICroom H503 abstract: We introduce connection, torsion and curvature for Courant algebroids. We discuss in detail torsionless connections compatible with a generalized metric and the related Einstein-Hilbert actions.

### 01.07.2015 (Wednesday)

#### Localization in Quiver Quantum Mechanics

Regular Seminar Kazutoshi Ohta (Meiji Gakuin University)

 at: 13:00 ICroom H503 abstract: We derive the localization formula for N=4 supersymmetric quiver quantum mechanics in the Higgs and Coulomb branch. The partition function (index) is exactly evaluated and it is shown that the path integral is localized at fixed points, which are given by solutions to the BRST equations combined with D-term and F-term conditions. We give various examples of the quiver theory and classifications of their fixed points. The indexes completely agree with the mathematical wall crossing formulae for the quiver moduli spaces. We also discuss a gravitational picture of the localization in the Coulomb branch.

### 24.06.2015 (Wednesday)

#### Defects and quantum Seiberg-Witten geometry

Regular Seminar Peter Koroteev (PI)

 at: 14:00 ICroom H503 abstract:

### 23.06.2015 (Tuesday)

#### Strings of 6d SCFTs

Regular Seminar Babak Haghighat (Harvard)

 at: 13:30 ICroom H503 abstract: We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.

### 08.06.2015 (Monday)

#### Warped Conformal Field Theory as Lower Spin Gravity

Regular Seminar Diego Hofman (UVA)

 at: 15:00 ICroom H503 abstract: Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non AdS space-times, including the near horizon geometry of generic extremal black holes. I’ll explain that WCFTs posses a type of boost symmetry. Using this insight, I’ll discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories will be discussed as well as examples of WCFTs. Lastly I’ll present a systematic description of the holographic duals of WCFTs. I’ll argue that the minimal setup is not Einstein gravity but an SL(2,R) x U(1) Chern-Simons Theory, which we call Lower Spin Gravity.

### 03.06.2015 (Wednesday)

#### Reconstructing holography as a RG flow

Regular Seminar Ayan Mukhopadhyay (CCTP and CCQCN, University of Crete)

 at: 14:00 ICroom H503 abstract: I will argue that the holographic correspondence can be reconstructed in the large N and strongly interacting limit as a specific generalisation of Wilsonian RG flow, which can be defined via three simple principles. I will also give an explicit example for such a reconstruction, where dual non-linear classical gravity equations in the long wavelength approximation will emerge from specific kinds of coarse graining of hydrodynamics in the field theory.

### 27.05.2015 (Wednesday)

#### Entanglement Entropy in Massive Quantum Field Theories

Regular Seminar Olalla Castro Alvaredo (City U.)

 at: 14:00 ICroom B1004 abstract: In this talk I will review some of the main results of my research in this area, which stated in 2007 in collaboration with John L. Cardy and Benjamin Doyon. I will emphasise how a special type of field we have named branch point twist field has become an essential tool for performing computations of the entanglement entropy in non-critical systems. I will show how the relationship between correlators of twist fields and entanglement entropy allows us to recover well-known results for critical systems but also to predict new results for theories with a finite correlation length. Time permitting, I will mention some more recent results extending our understanding to non-unitary critical and non-critical systems.

### 19.05.2015 (Tuesday)

#### Extremal chiral ring states in AdS/CFT are described by free fermions

Regular Seminar David Berenstein (UCSB)

 at: 13:30 ICroom B1004 abstract: Half BPS states (operators) in N=4 SYM are famously described by free fermions both at weak and strong coupling. I describe a set of conjectures for a preferred class of states in more general conformal field theories that can be tested in supergravity for when such a free fermion description might arise and some motivation for it applying generally. The states in question belong to the chiral ring of a supersymmetric conformal field theory that extremize an additional U(1) charge for fixed dimension and can be reduced to multi-traces of a composite matrix field, which is equivalent to using Young tableaux (Schur polynomials) as a basis. The main conjecture asserts that if the Young tableaux are orthogonal, then the set of extremal three point functions of traces to order 1/N are determined up to a single constant. The conjecture is extended further by providing an exact norm for the Schur basis and this norm arises from a set of free fermions for a generalized oscillator algebra.

### 12.05.2015 (Tuesday)

#### Entanglement entropy in a holographic model of the Kondo effect

Regular Seminar Mario Flory (Max-Planck Institute)

 at: 15:30 ICroom H503 abstract: My starting point is a holographic model of the Kondo effect recently proposed by Erdmenger et. al., i.e. of a magnetic impurity interacting with a strongly coupled system. Specifically, I focus on the challenges of computing gravitational backreaction in this model, which demands a study of the Israel junction conditions. I present general results on these junction conditions, including analytical solutions for certain toy models, that may be relevant also more generally in the AdS/boundary CFT correspondence. Furthermore, similar junction conditions for a bulk Chern-Simons field appearing in the holographic Kondo model are discussed. I then focus on the computation and interpretation of entanglement entropy in this holographic model.

### 30.04.2015 (Thursday)

#### Correlation functions of conserved currents in 3-dimensional superconformal theories

Exceptional Seminar Evgeny Buchbinder (University of Western Australia)

 at: 14:00 ICroom H503 abstract:

### 29.04.2015 (Wednesday)

#### Supersymmetric gauge theories on five-manifolds

Regular Seminar Paul Richmond (Oxford)

 at: 14:00 ICroom B1004 abstract: I will discuss how to construct rigid supersymmetric gauge theories on Riemannian five-manifolds following a holographic approach. This approach realises the five-manifold as the conformal boundary of a six-dimensional bulk supergravity solution and leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. The background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Finally, I’ll also construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.

### 18.03.2015 (Wednesday)

#### Partition function on Hopf surfaces and Casimir energy

Regular Seminar Benjamin Assel (Kings College)

 at: 14:00 ICroom H503 abstract: I will discuss the partition function of 4d N=1 theories on Hopf surfaces. These are diffeomorphic to S^1 x S^3 and the partition function provides a path integral realization of the supersymmetric index. Its large S^1 limit exhibits a universal behaviour associated to the existence of a Casimir energy. I will argue that, contrarily to the non-supersymmetric case, this Casimir energy is a physical (non-ambiguous) quantity in supersymmetric theories.

### 04.03.2015 (Wednesday)

#### Lessons from crossing symmetry at large N

Regular Seminar Tomasz Lukowski (Oxford)

 at: 14:00 ICroom H503 abstract: In this talk I will discuss how to construct all solutions consistent with crossing symmetry in the limit of large central charge c ~ N^2, starting from the four-point correlator of the stress tensor multiplet in N=4 SYM. Unitarity forces the introduction of a scale \Delta_{gap} and these solutions organize as a double expansion in 1/c and 1/\Delta_{gap}. These solutions are valid to leading order in 1/c and to all orders in 1/\Delta_{gap} and reproduce, in particular, instanton corrections previously found. Comparison with such instanton computations allows to fix \Delta_{gap}. Using this gap scale one can explain the upper bounds for the scaling dimension of unprotected operators observed in the numerical superconformal bootstrap at large central charge.

### 25.02.2015 (Wednesday)

#### Supergravity as a Consistent Quantum Theory?

Regular Seminar Tristan Dennen (NBI)

 at: 14:00 ICroom H503 abstract: Supergravity theories were once hoped to provide ultraviolet finite theories of quantum gravity without requiring profoundly new physical frameworks. These hopes faded in the 1980s, but renewed efforts in recent years have uncovered some surprising ultraviolet behaviour. In this talk, I will give an overview of the explicit scattering amplitude calculations in perturbative supergravity over the last few years. In particular cases, there are indications of ultraviolet cancellations not accounted for by known symmetry arguments. I will highlight these cases and give some reasons to be optimistic and some reasons to be pessimistic about supergravity as a contender for a quantum theory of gravity.

### 18.02.2015 (Wednesday)

#### lambda-deformations

Regular Seminar Kostas Sfetsos (University of Athens)

 at: 14:00 ICroom H503 abstract: We review the construction of the so-called λ-deformations of WZW and gauged WZW models. We discuss their integrability and algebraic properties, their behavior under RG flows as well as their embeddings to type-II supergravity.

### 12.02.2015 (Thursday)

#### Constraining Asymptotically Safe Inflation with cosmological observations

Exceptional Seminar Alfio Bonanno (INAF/INFN)

 at: 12:00 ICroom H503 abstract: