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)

20.03.2024 (Wednesday)

Modular Constraints on N=4 Yang-Mills / Type IIB Superstring Holography

Regular Seminar Daniele Dorigoni (Durham)

at:
14:00 IC
room H503
abstract:

I will describe a surprisingly simple representation of a class of integrated correlation functions of four superconformal primaries in the stress tensor multiplet of N=4 supersymmetric Yang-Mills theory with arbitrary simple gauge group, G. I then present exact formulae for these integrated correlators which are manifestly invariant under GNO electro-magnetic duality. For classical gauge groups, G=SU(N), SO(N), USp(2N), In the large-N limit these correlators are interpreted via holography in terms of the low-energy expansion of type IIB superstring amplitudes in AdS_5XS^5 or an orientifold thereof. In this way I recover the SL(2,Z)-invariant BPS interactions, arising in type IIB superstring amplitudes in the flat-space limit. From the asymptotic nature of the 1/N expansion I furthermore reconstruct non-perturbative contributions which holographically correspond to (p,q)-string world-sheet instantons.

06.03.2024 (Wednesday)

Exploring thermal CFTs

Regular Seminar Elli Pomoni (DESY)

at:
14:00 IC
room H503
abstract:

QFT at finite temperature can be studied via compactifying the time direction. Placing CFTs on this non-trivial manifold, a subgroup of conformal symmetries is broken. Nonetheless, it is possible to derive broken Ward identities, which provide novel constraints on the theory. These constraints not only systematically reproduce all known results, including an implicit formulation of the generalized Cardy formula, but also relate the thermal energy spectrum with the conformal spectrum. Moreover, novel sum rules for one-point functions of operators are derived. They allow the computation of one-point functions for light operators in terms of zero temperature data, as well as their asymptotic behavior for heavy operators.

05.03.2024 (Tuesday)

The String Landscape and the Swampland

Regular Seminar Miguel Montero (IFT/UAM)

at:
14:30 IC
room H503
abstract:

It is natural to expect that quantum gravity is not directly relevant at the low energies which experimentally accesible today, since the Planck scale is many orders of magnitude above the electroweak scale. However, mounting evidence coming from String Theory compactifications, general considerations based on black hole evaporation and holography suggest that there are some constraints that must be satisfied by low-energy effective field theories coupled to Einsteinian gravity. These constraints can in principle be used to rule out models at low energies or to connect with observations, an effort dubbed the "Swampland Program". I will review the program, its motivation, and recent advances.

28.02.2024 (Wednesday)

Anomalies and Gauging of U(1) Symmetries

Regular Seminar Francesco Benini (SISSA)

at:
14:00 IC
room H503
abstract:

The Symmetry TFT of a quantum field theory is a Topological Field Theory in one dimension more, that describes the structure of the symmetry, its representations, its anomalies, and the possible topological manipulations (gaugings). Until recently only the case of finite symmetries had been addressed. I will present a proposal for the Symmetry TFT of theories with a U(1) symmetry: it is a BF theory with a continuum of topological operators. I will discuss many examples, including chiral anomalies, 2-groups, the non-invertible Q/Z chiral symmetry in 4d with ABJ anomaly, and I will discuss the non-Abelian case as well.

27.02.2024 (Tuesday)

Infinite Permutation Groups and the Origin of Quantum Mechanics

Regular Seminar Pavlos Kazakopoulos (U Athens)

at:
14:30 IC
room BLKT 741
abstract:

In this talk, we examine a fundamental question posed some time ago by Birkhoff and von Neumann: What are the possible structures of measurement in a theory of Physics? We find striking connections with the conceptual framework of First Order Logic, and apply classification theorems for the automorphism groups of first order relational structures to argue for the uniqueness of Hilbert space as the phase space of a theory with probabilistic transitions between atomic states. We discuss possible applications of these observations to Algebraic Quantum Field Theory.

21.02.2024 (Wednesday)

Dimensionally Reducing Generalized Symmetries from (3+1)-Dimensions

Regular Seminar Gabi Zafrir (University of Haifa)

at:
14:00 IC
room H503
abstract:

Recently there has been a renewed interest in the subject of novel types of symmetries, now known as generalized symmetries. An interesting question is what happens to these more general symmetry structures upon compactification to lower dimensions. In this talk, we shall explore this in the context of the compactification of 4d N=1 SCFTs to 2d on spheres.

14.02.2024 (Wednesday)

The AdS Virasoro-Shapiro amplitude

Regular Seminar Tobias Hansen (Durham University)

at:
14:00 IC
room H503
abstract:

I will present a constructive method to compute the Virasoro-Shapiro amplitude on AdS5xS5, order by order in AdS curvature corrections. The k-th curvature correction takes the form of a genus zero world-sheet integral involving single-valued multiple polylogarithms of weight 3k. The coefficients in an ansatz in terms of these functions are fixed by Regge boundedness of the amplitude, which is imposed via a dispersion relation in the holographically dual CFT. We explicitly constructed the first two curvature corrections. Our final answer reproduces all CFT data available from integrability and all localisation results, to this order, and produces a wealth of new CFT data for planar N=4 SYM theory at strong coupling. Finally, the high energy limit of the AdS Virasoro-Shapiro amplitude is compared to a classical scattering computation in AdS and agreement is found.

13.02.2024 (Tuesday)

Crystalline topological matter in and out of equilibrium

Colloquium Frank Schindler (Imperial College London)

at:
14:30 IC
room H503
abstract:

I’ll give a pedagogical introduction to some conceptual aspects of quantum materials in and out of equilibrium. Such materials, capable of realising exotic states of matter, hold promise for manifold applications in areas like microelectronics and quantum computing. The most basic quantum materials are electronic band insulators. My talk will start with an explanation of how they can be categorised based on crystalline symmetry and topology. Following this, I will broaden the framework of band topology to include non-Hermitian Hamiltonians, which describe systems that are not in equilibrium. To conclude my talk, I will delve into a curious connection between Hermitian bulk and non-Hermitian boundary topological invariants.

06.02.2024 (Tuesday)

Higher-twist Regge trajectories in CFTs

Colloquium Petr Kravchuk (King's College London)

at:
14:30 IC
room H503
abstract:

Abstract: On general grounds, the spectrum of a Conformal Field Theory (CFT) is expected to be extremely complicated away from special limits. One of such limits consists of the lowest energy states for every given spin, which are also known as the leading-twist states. In this talk I will discuss the structures that emerge in the spectrum as one departs from this limit towards the higher-twist states, focusing especially on the Regge trajectories. In particular, I will describe a general mechanism that reconciles the idea of Regge trajectories with the growing number of local operators at large spin. I will then demonstrate how this mechanism works in the case of one-loop phi^4 Wilson-Fisher theory in epsilon-expansion. This example will also clarify the properties of double-twist trajectories and light-cone bootstrap at higher-twist. Finally, I will briefly discuss a work in progress on going beyond the double-twist limit.

31.01.2024 (Wednesday)

On the class S origin of discs and spindles

Regular Seminar Pieter Bomans (Oxford)

at:
14:00 IC
room H503
abstract:

In this talk, we delve into the world of spindle and disc solutions dual to 4d SCFTs. Despite extensive studies conducted over the years, certain aspects continue to challenge our understanding. Disc solutions, conjectured to be dual to Argyres-Douglas theories, present a puzzle as at first sight the symmetries do not match across the holographic correspondence. The spindle solutions, on the other hand, completely lack a proper understanding of their dual field theories. This talk aims to shed light on these puzzles, offering a detailed explanation for the breaking of the unwanted symmetry in disc solution. Furthermore, we will clarify various aspects of the spindle solution, contributing to a more profound understanding of the class S origin of the dual SCFTs. As a byproduct, we enlarge the class of holographic surface defects of the (2,0) theory as well as provide a concrete description of a class of locally N=1 preserving punctures.

24.01.2024 (Wednesday)

Probing the deep string spectrum

Regular Seminar Chrysoula MARKOU (University of Mons)

at:
14:00 IC
room H 503
abstract:

As is well known, the string spectrum comprises infinitely many states that can collectively be visualized along Regge trajectories of increasing mass and spin. Its massless and lightest levels, as well as certain higher spins including the leading Regge trajectory, have been the focus of past studies. In principle, access to any state is possible, but the traditional methodology is non-covariant and does not immediately lead to irreducible representations of the Wigner little group. In this talk, we will discuss a new and covariant technology of constructing the string spectrum. It is based on the observation that there is a bigger symmetry behind the Virasoro constraints: the symplectic algebra that commutes with the spacetime Lorenz algebra. This enables excavating string states and their interactions by entire trajectories, rather than individually.

15.01.2024 (Monday)

Some Aspects of Krylov Complexity

Regular Seminar Eliezer Rabinovici (Hebrew University of Jerusalem)

at:
15:00 IC
room H503
abstract:

A review of the concept of Krylov Complexity(K- Complexity) will be presented. One feature of K-Complexity is that its definition does not involve a tolerance parameter. I will describe some general properties of K-Complexity, its behavior when interpolating among various types of systems: free, strongly integrable and chaotic ones. Finally for a certain low dimensional system in a certain state I will describe an explicit derivation of the geometric bulk dual of K complexity.

13.12.2023 (Wednesday)

From conformal to confining QFTs

Regular Seminar Ali Fatemiabhari (Swansea University)

at:
14:00 IC
room Huxley 503
abstract:

In this talk, I present new solutions for type IIB supergravity generated by an infinite family of uplifts from six-dimensional supergravity solutions. After compactification on a circle, I will discuss that these backgrounds are proposed to be holographically dual to confining Quantum Field Theories. In the high energies, field theories will approach the strongly coupled regime of 5d quiver gauge field theories. I also mention some observables like Wilson loops and Entanglement entropy to sketch the properties of the theories.

04.12.2023 (Monday)

Finding isomorphic superconformal field theories

Regular Seminar Monica Kang (Caltech)

at:
14:00 IC
room Huxley 503
abstract:

When do two different looking quantum field theories describe the same physics? This is essentially asking when the quantum field theories are isomorphic. In the case of topological quantum field theories, there are sometimes a way to determine them via topological invariants. For a superconformal field theory, what would be the minimal set of “invariants” to determine when they are isomorphic? I will discuss some approaches to this question in the context of superconformal field theories in four and six dimensions. Utilizing 4d class S theories that also admits 6d (1,0) SCFT origins, I will explain how a certain class of 4d N=2 SCFTs, which a priori look like distinct theories, can be shown to describe the same physics. I will further explain how the 6d (1,0) origin sheds light on the 3d duality.

29.11.2023 (Wednesday)

Higher-order gravities: What they are and what they are for

Regular Seminar Angel Murcia (University of Padova)

at:
14:00 IC
room Huxley 503
abstract:

Higher-order gravities are extensions of General Relativity (GR) which introduce in the classical action terms of higher order in the curvature. These appear naturally in the context of string effective actions, as well as in generic gravitational EFTs. Among the myriads of higher-order gravities one may think of, in this talk I will focus on specific theories whose equations of motion are of second order in derivatives for some particular backgrounds. I will provide many examples of such theories, classification results and argue that a subclass of them actually forms a basis for the space of gravitational EFTs. Afterwards, I will discuss the addition of non-minimal couplings to matter, show that some of these theories possess fully regular black hole solutions and conclude with some holographic applications.

23.11.2023 (Thursday)

Equivalence of 1-loop RG flows in 4d Chern-Simons and integrable 2d sigma-models

Exceptional Seminar Nat Levine (ENS Paris)

at:
13:00 IC
room Huxley 711C
abstract:

Costello, Witten and Yamazaki proposed a 4d Chern-Simons theory as a unified way to engineer integrable models. In the presence of 'Disorder' defects (for non-ultralocal 2d theories), this correspondence has been established only classically. As a first quantum check, I will derive the matching of 1-loop divergences between the 4d and 2d theories. My assumptions are general and seem to isolate sigma-models among the 2d theories. (Based on 2309.16753)

22.11.2023 (Wednesday)

Finite-N Black Hole Cohomologies

Regular Seminar Siyul Lee (Michigan University)

at:
14:00 IC
room Huxley 503
abstract:

We study new cohomologies for the BPS operators of the N=4 Yang-Mills theory with SU(2), SU(3) and SU(4) gauge groups. The goal of this programme is to identify the black hole microstates in the dual field theory that are successfully counted by the index to match the Bekenstein-Hawking entropy. We first study the index over non-graviton cohomologies and identify their threshold levels. We present examples of the non-graviton operators in the SU(2) theory and in a subsector of the SU(3) theory that corresponds to the BMN matrix model. We also present an ansatz that can be used to construct these operators. Finally, we discuss non-trivial tower structures and partial no-hair behaviours of quantum black holes.

15.11.2023 (Wednesday)

The Statistical Interpretation of Semi-Classical Gravity

Triangular Seminar Jan de Boer (University of Amsterdam)

at:
15:00 IC
room Lecture Theatre 3, Blackett building
abstract:

I this talk I will describe a picture which has emerged over the past few years regarding the statistical interpretation of semiclassical gravity and how this relates to wormholes, averaging and the so-called factorization puzzle, the information paradox, and a combinatorial description of 3d gravity.

15.11.2023 (Wednesday)

A tensor model for chaotic CFT

Triangular Seminar Julian Sonner (University of Geneva)

at:
16:30 IC
room Lecture Theatre 3, Blackett building
abstract:

I will describe a novel class of statistical ensembles we developed for the description of chaotic conformal field theories. These are generalisations of the usual random-matrix type theories used in the description of quantum chaotic many-body systems, and implement the kinematical as well as dynamical constraints of the CFT bootstrap. These novel statistical models take the form of distributions over random matrices and tensors. I will take some time to characterise the individual elements in terms of so-called “approximate CFTs”. Finally, I will discuss the concrete realisation of these ideas for 2D, large-c CFT and point out that the resulting tensor models (subject to reasonable constraints on the spectrum) take the form of an integral over random discrete triangularisation of 3D Euclidean manifolds, governed by the 6j symbols of Virasoro, strongly suggesting a connection to three dimensional quantum gravity.

08.11.2023 (Wednesday)

BPS Ensembles

Regular Seminar Yoav Zigdon (University of Cambridge)

at:
14:00 IC
room Huxley 503
abstract:

We study ensembles of half-BPS bound states of fundamental strings and NS-fivebranes (NS5-F1 states) in the decoupling limit. We revisit a solution corresponding to an ensemble average of these bound states, and find that the appropriate duality frame for describing the near-source structure is the T-dual NS5-P frame in which the fivebranes are generically well-separated; this property results in the applicability of perturbative string theory. The geometry sourced by the typical microstate is not close to that of the black hole that carries the same charges. When members of the ensemble spin with two fixed angular potentials about two orthogonal planes, we find that the ensemble average geometry has an ellipsoidal structure. This contrasts with ring structures obtained when fixing the angular momenta instead of the angular potentials; we trace this difference of ensembles to large fluctuations of the angular momentum in the ensemble of fixed angular potential.