## 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)

### 16.10.2019 (Wednesday)

#### TBA

Regular Seminar Davide Cassani (INFN Padua)

 at: 14:00 ICroom H503 abstract:

### 09.10.2019 (Wednesday)

#### TTbar and TsT

Regular Seminar Stijn van Tongeren (Humboldt U)

 at: 14:00 ICroom H503 abstract: The TTbar deformation of two dimensional QFTs has various attractive and interesting features, giving a simple CDD deformation of the S matrix, and for instance preserving integrability, if present. As a simple example, deforming massless free scalars gives a Nambu-Goto string in flat space in a uniform light-cone gauge. I will discuss what happens if we deform "twice", i.e. TTbar deform light-cone gauge fixed string sigma models. In this setting, TTbar deformations can be viewed as TsT transformations in a suitable T dual frame. This TsT picture also gives a natural interpretation of the TTbar CDD factor as a Drinfeld-Reshetikhin twist.

### 08.10.2019 (Tuesday)

#### TBA

Regular Seminar K Narayan (Chennai Mathematical Institute)

 at: 14:00 ICroom H602 abstract:

### 02.10.2019 (Wednesday)

#### Localization of 4d N=1 theories on D2 x T2

Regular Seminar Antonio Pittelli (Uppsala)

 at: 14:00 ICroom H503 abstract: We consider 4d N=1 gauge theories with R-symmetry on a hemisphere times a torus. We apply localization techniques to evaluate the exact partition function through a cohomological reformulation of the supersymmetry transformations. Our results represent the natural elliptic lifts of the lower dimensional analogs as well as a field theoretic derivation of the conjectured 4d holomorphic blocks, from which partition functions of compact spaces with diverse topology can be recovered through gluing. We also analyze the different boundary conditions which can naturally be imposed on the chiral multiplets, which turn out to be either Dirichlet or Robin-like. We show that different boundary conditions are related to each other by coupling the bulk to 3d N=1 degrees of freedom on the boundary three-torus, for which we derive explicit 1-loop determinants.

### 26.06.2019 (Wednesday)

#### The entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole

Regular Seminar Henry Maxfield (UCSB)

 at: 14:00 ICroom H503 abstract: Semiclassical gravity is famously in tension with the unitary evolution of quantum mechanics when black holes evaporate. I'll describe a semiclassical calculation that nonetheless reproduces signatures of unitarity, namely the "Page curve" of entropy and the Hayden-Preskill protocol. This involves finding a quantum extremal surface, an extremum of the generalised entropy (the area in Planck units plus the entropy of exterior matter), which in the context of an evaporating black hole can exist far from a classical extremal surface. The calculations are performed in an exactly solvable model of Jackiw-Teitelboim gravity coupled to conformal matter. I will conclude by commenting and speculating on the implications for the information paradox.

### 12.06.2019 (Wednesday)

#### Euclidean Wormholes and Holography

Regular Seminar Panos Betzios (Crete)

 at: 14:00 ICroom H503 abstract: In this talk I will discuss asymptotically AdS wormhole solutions in the context of holography. I will present how to compute correlation functions of local operators as well as non local observables such as correlation functions of Wilson loops on the distinct boundaries and I will discuss their behavior. Moreover, I will discuss the effect that multi-trace deformations have on such observables. From the computations mentioned we observe that the dual theory is expected to be described in terms of two interacting sectors coupled by a UV soft, non-local interaction. Finally, I will present a simple effective field theory construction that can explain the behaviors that we observe from these gravitational computations.

### 05.06.2019 (Wednesday)

#### Black holes in N=4 Super-Yang-Mills

Regular Seminar Francesco Benini (SISSA)

 at: 14:00 ICroom H503 abstract: AdS/CFT provides a consistent non-perturbative definition of quantum gravity in asymptotically AdS space. Black holes should correspond to ensembles of states in the boundary field theory. By analyzing the superconformal index of 4d N=4 SU(N) Super-Yang-Mills, with the help of a new Bethe Ansatz type formula, we are able to exactly reproduce the Bekenstein-Hawking entropy of BPS black holes in AdS5 x S5. The large N limit exhibits many competing contributions and Stokes phenomena, hinting at new physics.

### 04.06.2019 (Tuesday)

#### Bimetric theory of fractional quantum Hall states

Regular Seminar Andrey Gromov (Brown)

 at: 13:30 ICroom H503 abstract: Fractional quantum Hall (FQH) states are topologically ordered. Additionally, FQH states support a collective neutral excitation known as the Girvin-MacDonald-Platzman (GMP) mode. Certain features of this mode are independent of the microscopic details. The objective of the talk is to construct an effective theory includes both topological properties and the massive GMP mode. The theory reproduces the universal properties of chiral lowest Landau level (LLL) FQH states which lie beyond the TQFT data, such as the projected static structure factor and the GMP algebra of area-preserving diffeomorphisms. The dynamics of the mode is described by a fluctuating rank-2 symmetric, positive-definite tensor, which leads to a natural geometric (or gravitational) interpretation of the GMP mode.

### 29.05.2019 (Wednesday)

#### TBA

Regular Seminar Chris Blair (VUB)

 at: 14:00 ICroom H503 abstract: TBA

### 22.05.2019 (Wednesday)

#### Little Strings, Long Strings, and Fuzzballs

Regular Seminar Emil Martinec (Chicago)

 at: 14:00 ICroom H503 abstract: The microstate structure of AdS3 black holes involves stringy ingredients, yet quantitative control over these ingredients in a regime where the state being described approximates a black hole has been elusive. This talk will show how 2d worldsheet current algebra provides a tool to describe the stringy objects that govern the black hole phase transition in AdS3 and linear dilaton backgrounds, providing a bridge between the entropy-carrying degrees of freedom of the dual non-gravitational theory (little strings or long strings) and their conjectured gravitational dual, the fuzzball.

### 15.05.2019 (Wednesday)

#### TBA

Regular Seminar Vasileios Niarchos (Durham)

 at: 14:00 ICroom H503 abstract:

### 08.05.2019 (Wednesday)

#### Duality invariant cosmology to all orders in alpha prime

Regular Seminar Olaf Hohm (Humboldt, Berlin)

 at: 14:00 ICroom H503 abstract: I discuss the higher-derivative \alpha' corrections in the reduction to one dimension (cosmic time) that is relevant for the dynamics of cosmological backgrounds. In this setting string theory is known to be duality invariant under O(d,d), which makes it possible to completely classify all \alpha' corrections. I discuss some generic features of the \alpha' completed Friedmann equations and show that there are duality invariant theories that allow for de Sitter solutions that are non-perturbative in \alpha', suggesting that string theory may permit de Sitter vacua in this novel fashion.

### 01.05.2019 (Wednesday)

#### TBA

Regular Seminar Wout Merbis (ULB)

 at: 14:00 ICroom H503 abstract:

### 10.04.2019 (Wednesday)

#### Looking for Partially-Massless Gravity

Regular Seminar Karapet Mkrtchyan (Potsdam)

 at: 14:00 ICroom H503 abstract: We study the possibility for a unitary theory of partially-massless (PM) spin-two field interacting with Gravity in arbitrary dimensions. We show that parity invariant interactions respecting general covariance lead to a reconstruction of Conformal Gravity in even dimensions. In this case the unitarity is sacrificed. By relaxing the parity invariance, we find a possibility of a unitary theory in four dimensions, but the parity-odd cubic vertex cannot be written in usual metric variables. We comment on possible approaches that may allow for the formulation of this theory. Finally, by relaxing the general covariance, we show that a non-minimal coupling between massless and PM spin-two fields may lead to an alternative possibility of a unitary theory, that necessarily involves mixed-symmetry fields.

### 02.04.2019 (Tuesday)

#### TBA

Regular Seminar Andreas Albrecht (UC Davis)

 at: 13:30 ICroom H503 abstract:

### 27.03.2019 (Wednesday)

#### Infrared enhancement of supersymmetry in four dimensions

Regular Seminar Simone Giacomelli (Oxford)

 at: 14:00 ICroom H503 abstract: In this seminar I will discuss a recently-found class of RG flows in four dimensions exhibiting enhancement of supersymmetry in the infrared, which provides a lagrangian description of several strongly-coupled N=2 SCFTs. The procedure involves starting from a N=2 SCFT, coupling a chiral multiplet in the adjoint representation of the global symmetry to the moment map of the SCFT and turning on a nilpotent expectation value for this chiral. We show that, combining considerations based on 't Hooft anomaly matching and basic results about the N=2 superconformal algebra, it is possible to understand in detail the mechanism underlying this phenomenon and formulate a simple criterion for supersymmetry enhancement.

### 26.03.2019 (Tuesday)

#### TBA

Regular Seminar Sergej Moroz (TU Munich)

 at: 13:30 ICroom H503 abstract:

### 19.03.2019 (Tuesday)

#### TBA

Regular Seminar Andres Collinucci (ULB)

 at: 13:30 ICroom H503 abstract:

### 15.03.2019 (Friday)

#### Integrability, Poisson-Lie Symmetry and Double Field Theory

Regular Seminar Hassler Falk (University of Oviedo)

 at: 14:00 ICroom SAF 119 abstract: I review how integrability allows us to explore the planar limit of the AdS/CFT correspondence for arbitrary values of the t'Hooft coupling. In string theory integrability of the 2D σ-model is closely related to Poisson-Lie Symmetry. Double Field Theory can be used to make this symmetry manifest and therewith provides a new tool to study the implications for the gravity side of the correspondence.

### 13.03.2019 (Wednesday)

#### Holographic Complexity in Vaidya Spacetimes

Regular Seminar Shira Chapman (University of Amsterdam)

 at: 14:00 ICroom H503 abstract: We investigate holographic complexity for eternal black hole backgrounds perturbed by shock waves, with both the complexity=action (CA) and complexity=volume (CV) proposals. We consider Vaidya geometries describing a thin shell of null fluid with arbitrary energy falling in from one of the boundaries of a two-sided AdS-Schwarzschild spacetime. We demonstrate how scrambling and chaos are imprinted in the complexity of formation and in the full time evolution of complexity via the switchback effect for light shocks, as well as analogous properties for heavy ones.