## 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)

### 16.11.2020 (Monday)

#### LonTI: Branes and the moduli space of instantons

Regular Seminar Amihay Hanany (IC)

 at: 10:30 ICroom Zoom abstract: This is the live session included as part of the LonTI lecture on Branes and the moduli space of instantons. Please register at https://lonti.weebly.com/registration.html to receive joining instructions for this live session which will be held via Zoom. Instantons, or solutions to the self dual Yang Mills (SDYM) equations are well known solutions, introduced in the mid 70s and played a role in a host of applications in QFT and String Theory. This talk will show a simple brane construction which allows the computation of the moduli space of solutions to the SDYM equations, introduce the student to the world of quivers, and demonstrate simple computations which allow evaluations of these moduli spaces. â€‹

### 10.11.2020 (Tuesday)

#### Closed strings and weak gravity condition from higher-spin causality

Regular Seminar Sandipan Kundu (Johns Hopkins University)

 at: 13:30 ICroom zoom 871 9223 5980 abstract: I will show that metastable higher spin particles, free or interacting, cannot couple to gravity while preserving causality unless there exist higher spin states in the gravitational sector much below the Planck scale. Causality imposes an upper bound on the mass of the lightest higher spin particle in the gravity sector in terms of quantities in the non-gravitational sector. I will argue that any weakly coupled UV completion of such a theory must have a gravity sector containing infinite towers of asymptotically parallel, equispaced, and linear Regge trajectories. This implies that the gravity sector has a stringy structure with an upper bound on the string scale. Another consequence of this bound is that all metastable higher spin particles in 4d with masses below the string scale must satisfy a weak gravity condition. Moreover, these bounds also have surprising implications for large N QCD coupled to gravity and cosmology. [please email a.held@imperial.ac.uk for zoom link or password]

### 03.11.2020 (Tuesday)

#### Dark Energy and String Theory

Regular Seminar Susha Parameswaran (University of Liverpool)

 at: 13:30 ICroom zoom 871 9223 5980 abstract: I will give a (biased) review on the main current ideas to explain the fundamental nature of Dark Energy using string theory. The possibility of a de Sitter vacuum in string theory, corresponding to a cosmological constant with w=-1, has proven difficult to achieve, leading to the conjecture that such vacua might lie in the String Theory Swampland. Other interesting string candidates include axion or runaway quintessence. I will in particular discuss the Thermal Dark Energy proposal. Here finite temperature effects in a light hidden sector hold a hidden scalar away from the minimum of its zero-temperature potential, leading to an effective cosmological constant, consistently with the Swampland Conjectures and with potentially observable consequences. [please email a.held@imperial.ac.uk for zoom link or password]

### 28.10.2020 (Wednesday)

#### Non-perturbative physics for JT gravity and supergravity

Triangular Seminar Clifford Johnson (USC)

 at: 16:00 ICroom Zoom -- instructions in abstract abstract: Jackiwâ€“Teitelboim (JT) gravity and supergravity theories are exciting solvable models that teach us about low temperature black hole dynamics, and aspects of quantum chaotic behaviour. They have been shown (by Saad, Shenker and Stanford, and by Stanford and Witten) to have double scaled random matrix model descriptions, capturing the (spacetime) topological perturbative expansion of the partition function. I will describe an alternative method for building the matrix model description, using techniques from minimal string theory. This method is particularly useful for supplying non-perturbative definitions of the physics. I show how this allows for the computation of key aspects of the physics at low energy and temperature. For the zoom link, please email antoine.brgt@gmail.com

### 27.10.2020 (Tuesday)

#### Moduli stars

Regular Seminar Francesco Muia (Theory Group DESY)

 at: 13:30 ICroom zoom 871 9223 5980 abstract: The recent direct detection of gravitational waves (GWs) has opened a new window of observation for physical phenomena in which gravity is the dominant interaction. Collisions of black holes and neutron stars have been observed and a plethora of new events, even involving new physics, are expected to be detected in the next few years. It is natural to explore alternative physical objects that may exist which are different from the standard stars and black holes and that could lead to particular imprints on the GW spectrum. In this talk I will explore the possibility that moduli (gravitationally coupled scalar fields arising in all string compactifications) can compose star-like objects (moduli stars) whose dynamics gives rise to GW production. I will illustrate their formation in the early universe, that has been studied through lattice techniques. After their formation moduli stars can have different behaviours, e.g. they could rapidly collapse to black holes or disperse into scalar radiation, resulting in different phenomenology. I will describe the fate of moduli stars, that has been investigated through numerical relativity techniques. [please email a.held@imperial.ac.uk for zoom link or password]

### 20.10.2020 (Tuesday)

#### Pushing the limits of the double copy

Regular Seminar Mariana Carrillo (Imperial College London)

 at: 13:30 ICroom zoom 871 9223 5980 abstract: The double copy in its original form allows us to obtain scattering amplitudes of gravity as the "square" of those of Yang Mills. I will explain how this squaring procedure works and how this relationship has been extended to classical solutions. I will also briefly mentioned how the double copy relationship can be extended to scalar effective field theories. [please email a.held@imperial.ac.uk for zoom link or password]

### 20.10.2020 (Tuesday)

#### Integrable deformations and the doubled formalism

Regular Seminar Yuta Sekiguchi (Imperial College London)

 at: 14:00 ICroom zoom 871 9223 5980 abstract: The integrable deformation of string backgrounds has been one of the significant research directions to construct a variety of examples of gauge/gravity duality preserving integrability and to push forward the confirmation of AdS/CFT correspondence. In this introductory talk, I plan to give a basic review of classical integrability of string sigma models with a focus on Lax pairs, to consider the role of the doubled sigma model. [please email a.held@imperial.ac.uk for zoom link or password]

### 13.10.2020 (Tuesday)

#### Deforming integrable symmetries

Regular Seminar Fiona Seibold (Imperial College London)

 at: 13:30 ICroom zoom 871 9223 5980 abstract: Integrable models are the cornerstones of theoretical physics, simple enough to be solved exactly and yet rich enough to offer a glimpse into the dynamics of more intricate systems. Also two-dimensional field theories or string theories can be integrable. In this talk I will discuss integrability in field and string theories and present a special class of integrable models that promote the symmetry algebra of the undeformed theory to a quantum group. [please email a.held@imperial.ac.uk for zoom link or password]

### 13.10.2020 (Tuesday)

#### Supersymmetry and Computation

Regular Seminar Marcos Crichigno (Imperial College London)

 at: 14:00 ICroom zoom 871 9223 5980 abstract: I will discuss some aspects of supersymmetric systems from a computational perspective. [please email a.held@imperial.ac.uk for zoom link or password]

### 06.10.2020 (Tuesday)

#### Courant algebroids, Poisson-Lie T-duality and supergravity (of type II)

Regular Seminar Fridrich Valach (Imperial College London)

 at: 13:30 ICroom zoom abstract: Description: Courant algebroids provide a natural framework for working with the low energy limits of string theory. In particular, they are well suited for the study of Poisson-Lie T-duality, which is a generalization of the usual T-duality. We will discuss how to see bosonic fields of type II supergravity as structures on Courant algebroids (generalized metrics, spinors and divergence operators). We will then construct appropriate curvature tensors and use them to prove the compatibility of Poisson-Lie T-duality and the equations of motion of supergravity. The framework also allows us to use algebraic methods to search for new (non-isometric) string backgrounds. This is a joint work with Pavol Å evera. [please email a.held@imperial.ac.uk for zoom-link]

### 06.10.2020 (Tuesday)

#### Extended symmetries in field theory and gravity

Regular Seminar Karapet Mkrtchyan (Imperial College London)

 at: 14:00 ICroom zoom abstract: I will summarise my research interests and recent work, which is mainly related to the problems of field and gravity theories with extended symmetries. Such systems are the higher-spin and coloured gravity theories, theories of non-abelian chiral p-forms or partially-massless fields (satisfactory interacting theories of which are still missing). [please email a.held@imperial.ac.uk for zoom-link]

### 08.09.2020 (Tuesday)

#### Entanglement entropies of equilibrated pure states in quantum many-body systems and replica wormholes

Informal Seminar Hong Liu (MIT)

 at: 14:00 ICroom online - instructions in abstract abstract: We develop a universal approximation for the Renyi entropies of a pure state at late times in non-integrable systems, which macroscopically resembles an equilibrium density matrix. The resulting expressions are fully determined by properties of the associated equilibrium density matrix, and are hence independent of the details of the initial state, while also being manifestly consistent with unitary time-evolution. For equilibrated pure states in gravity systems, such as those involving black holes, this approximation gives a prescription for calculating entanglement entropies using Euclidean path integrals which is consistent with unitarity and hence can be used to address the information loss paradox of Hawking. Applied to recent models of evaporating black holes and eternal black holes coupled to baths, it provides a derivation of replica wormholes, and elucidates their mathematical and physical origins. In particular, it shows that replica wormholes can arise in a system with a fixed Hamiltonian, without the need for ensemble averages. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

### 04.08.2020 (Tuesday)

#### Gravity/Ensemble Duality

Informal Seminar Elizabeth Wildenhain (University of California, Berkeley)

 at: 16:00 ICroom online - instructions in abstract abstract: For the first time, a gravitational calculation was recently shown to yield the Page curve for the entropy of Hawking radiation, consistent with unitary evolution. However, the calculation takes as essential input Hawking's result that the radiation entropy becomes large at late times. We call this apparent contradiction the state paradox. We exhibit its manifestations in standard and doubly-holographic settings, with and without an external bath. We clarify which version(s) of the Ryu-Takayanagi prescription apply in each setting. We show that the two possible homology rules in the presence of a braneworld generate a bulk dual of the state paradox. The paradox is resolved if the gravitational path integral computes averaged quantities in a suitable ensemble of unitary theories, a possibility supported independently by several recent developments. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

### 28.07.2020 (Tuesday)

#### Wormholes and branes in JT gravity

Informal Seminar Andreas Blommaert (Ghent University)

 at: 14:00 ICroom online - instructions in abstract abstract: I will highlight the role of wormholes and branes in reconciling semiclassical gravitational (black hole) physics with unitary quantum mechanical evolution. Most of the talk will be based on recent developments in JT gravity. This is a model of quantum gravity in two dimensions which is analytically tractable. I will first explain why we need wormholes in order to capture late time properties of chaotic quantum systems from a geometrical point of view. I then point out that naively the inclusion of wormholes in a gravitational theory comes with an ensemble interpretation of said gravitational theory. Finally I will explain how this conclusion (that gravity is an ensemble) can be avoided by including branes in the bulk geometrical description. These branes can encode the micro structure of a given unitary quantum system in bulk geometry. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

### 21.07.2020 (Tuesday)

#### Superconformal RG Interfaces in Holography

Informal Seminar Matthew Cheung (Imperial College London)

 at: 14:00 ICroom online - instructions in abstract abstract: Defects/interfaces/boundaries are interesting objects to study in QFT, and one powerful way to study them is via the use of holography. In this talk, I will discuss our construction of gravitational solutions that holographically describe two different 4d SCFTs joined together at a co-dimension one, planar RG interface and preserving 3d superconformal symmetry. The RG interface we have constructed joins the 4d N=4 SYM theory on one side with the N=1 Leigh-Strassler SCFT on the other. These solutions in general are associated with spatially dependent mass deformations on the N=4 SYM side, but there is a particularly interesting solution for which these deformations vanish. If time allows, I will also discuss another example of our work involving ABJM theory and two 3d N=1 SCFTs with G_2 symmetry. This talk is based on the work hep-th/2007.07891 with Igal Arav, Jerome Gauntlett, Matt Roberts and Chris Rosen. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

### 23.06.2020 (Tuesday)

Regular Seminar Eugene Lim (King's College London)

 at: 13:30 ICroom online - instructions in abstract abstract: Inflation is now the paradigmatic theory of the Big Bang. But is it deserved? I will describe the conceptual and theoretical challenges that Inflation is still facing, argue that we should keep an open mind. In particular, I will argue that while it is a theory that claims to be a theory of initial conditions of the Universe, successful inflation actually depends on an intimate interplay between its own initial conditions and the inflationary model. I will show how one might go about probing this interplay by testing whether inflation can begin if its own initial conditions are not homogenous. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.

### 17.06.2020 (Wednesday)

#### On higher-spin theory in two dimensions

Regular Seminar Xavier Bekaert (Tours (France))

 at: 14:00 ICroom Zoom abstract: We aim at formulating a higher-spin gravity theory around AdS2 relevant for holography. As a first step, we investigate its kinematics by identifying the low-dimensional cousins of the standard higher-dimensional structures in higher-spin gravity such as the singleton, the higher-spin symmetry algebra, the higher-rank gauge and matter fields, etc.

### 11.06.2020 (Thursday)

#### Supersymmetric S-folds

 at: 15:45 ICroom Zoom abstract: I will discuss recent progress towards understanding geometric and holographic aspects of electromagnetic duality in four-dimensional supergravity. More concretely, I will focus on the connection between electromagnetic duality and the existence of new classes of supersymmetric S-fold backgrounds of type IIB supergravity. These provide natural candidates to holographically describe new strongly coupled three-dimensional CFTâ€™s which are localised on interfaces of N=4 super-Yang-Mills theory.

### 09.06.2020 (Tuesday)

#### A Quantum Lab for Quantum Field Theory

Regular Seminar Steven Abel (Durham University)

 at: 13:30 ICroom online - instructions in abstract abstract: In this pedagogical talk I will discuss recent and ongoing work showing how quantum field theory problems can be embedded on to quantum annealers. The general method we use is a discretisation of the field theory problem into a general Ising model, with the continuous field values being encoded into Ising spin chains. To illustrate the method, and as a simple proof of principle, we have used a quantum annealer to recover the correct profile of various tunnelling solutions. Then I will discuss current work where we construct actual quantum tunnelling processes involving instantons. These methods are applicable to many nonperturbative problems. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

### 03.06.2020 (Wednesday)

#### Spherical Branes, Supersymmetric Localization, and Holography

Regular Seminar Nikolay Bobev (KUL Leuven)

 at: 14:00 ICroom Zoom abstract: I will describe a class of supergravity solutions holographically dual to d-dimensional maximally supersymmetric SYM on S^d. Supersymmetric localization can be employed to calculate the partition function and the VEV of a 1/2-BPS Wilson lines in the planar limit of the SYM theory. I will present the results of this calculation and will show how they lead to a non-trivial precision test of holography in the context of non-conformal QFTs and space-times that are non asymptotically locally AdS.