Past Lecture Series

This page catalogues past speakers, along with the titles of their talks and their slides. Links to the videos will be shared on discord.

#12 Introduction to Asymptotic Symmetries

by Chandramouli Chowdhury (ICTS Bangalore)

Abstract: In these lectures, we will look at the subject of asymptotic symmetries and first review the subject in the book "Lectures on the Infrared Structure of Gravity and Gauge theories", by Andrew Strominger. We will first study the Generalized Noether Theorem, which will help us in analyzing the conserved charges of Gauge Symmetries. We will apply this to QED and Gravity in 4 dimensions and describe the abelian gauge symmetries in them. During this discussion, we will also introduce the Infrared Triangle and discuss the idea of memory effect and soft theorem.

Having reviewed the basics, we shall explore the story of Asymptotic symmetries in (even) higher dimensions and discuss the issues one faces while trying to generalize the story in gravity. We will then propose a novel resolution to these issues using some very simple constructs.

Link to Chandramouli's lecture notes are here.

#11 Universal Out of Equilibrium Physics

by Diptarka Das (IIT Kanpur)

Abstract: In these lectures we shall discuss universalities in non-equilibrium physics. A primary goal is to understand the late time fate of a closed quantum system subjected to out of equilibrium dynamics. Typically, systems exhibit thermalization, or at any rate some kind of equilibriation. To understand the fate is to identify the final ensemble that describes the system at late times. The other closely tied goal is to understand the mechanism that leads to the equilibriation. The physics becomes more interesting in presence of chaos, symmetry breakings and critical points. We will touch upon these various issues, while aiming to get some universal lessons in order to help build non-equilibrium intuition.

#10 TTbar and related deformations
by Soumangsu Chakraborty (TIFR, Mumbai)

Abstract: The Galilean field theories are developed to understand the low energy physics, where the velocity is very small compared to that of light. In this talk, I will look into the existence of action both for the magnetic and electric sectors of Galilean Electrodynamics using Helmholtz conditions. We prove the existence of unique action in magnetic limit with the addition of a scalar field in the system. The check also implies the non existence of action in the electric sector of Galilean electrodynamics. Further I will move on to the Dirac constraint analysis of the theory.

#9 Topological Quantum Field Theories

by Madhusudhan Raman

This lecture series provides an introduction to the topic of topological quantum field theories.

#8 Twistor Approach to N=4 SYM

by Arnab Priya Saha

This lecture series is based on this paper by Edward Witten.

#7 Renormalization Group and Polchinski equation

by Semanti Dutta

This lecture series is based on the paper Renormalization Group and Effective Lagrangians by Joseph Polchinski.

#6: Inversion formula in CFT

by Kausik Ghosh (IISc, Bangalore)

Abstract: Conformal field theory is characterised by the spectrum of local operators, i.e., typically the conformal dimension and spin. The set of OPE coefficient together with conformal dimension of all local operators is called CFT data. In a very nice paper Simon Caron Huot derived an interesting inversion formula which can compute the CFT data from the absorptive part of the four point correlators of scalars. This also gives a nice systematic way to compute large spin expansion. Furthermore this formula is analytic in spin in the similar spirit of Froissort-Gribov formula in massive field theories. This has found applications in many interesting problems that bootstrappers face very often.

In this lecture we will try to understand this formula.

#5: Celestial Holography: Scattering Amplitudes on the Celestial Sphere

by Sudip Ghosh (Okinawa Institute of Science and Technology)

Abstract: Recently Pasterski, Shao and Strominger have constructed a new basis of wavefunctions for describing asymptotic states in flat space scattering amplitudes. In this basis, D-dimensional S-matrix elements, also referred to as celestial amplitudes, transform as correlators of primary operators inserted on the (D-2)-dimensional celestial sphere at null infinity. This hints at the existence of a holographic correspondence between flat space scattering amplitudes and a putative dual celestial conformal field theory (CCFT) that lives on the celestial sphere.

See here for lecture notes.

#4: Infrared Divergences, Faddeev-Kulish States, and Asymptotic Symmetries

by Anupam A H (Institute of Mathematical Sciences)

Abstract: In the first of this series of three lectures, we introduce and construct Faddeev-Kulish (FK) states using the asymptotic Hamiltonian. In Lecture 2, we discuss the realisation of IR finite S-matrices in the FK formalism and work out an example at 1-loop level. . Finally, in Lecture 3, we discuss the relationship of FK states with asymptotic symmetries in gravity and QED.

#3: Double Copy Relations in Scattering Amplitudes

by PV Athira and A Manu (Chennai Mathematical Institute)

Abstract: In the first of this series of three lectures, we will discuss the Kawai-Lewellen-Tye relations, the statement of colour-kinematics duality, then discuss colour ordered amplitudes and discuss some examples. In Lecture 2, we discuss a short 1-loop example, and also the kinematic algebra in the MHV sector. Finally, in Lecture 3, we discuss the classical double copy and its relation to colour-kinematics duality.

#2: Review of JT Gravity / SYK Model Duality

by Adwait Gaikwad (Tata Institute of Fundamental Research)

Abstract: The goal of these lectures is to introduce the holographic duality between Sachdev-Ye-Kitaev (SYK) theory and Jackiw-Teitelboim (JT) gravity. We begin these set of lectures with introduction to JT gravity. We will study its classical and quantum analysis. After which we will introduce SYK theory and present the low energy effective action. In the final lecture we discuss the holographic dictionary.

#1: Introduction to Scattering Amplitudes from the Geometry of Polytopes

by Alok Laddha (Chennai Mathematical Institute)

Abstract: In these lectures, we will introduce some of the basic ideas that underlie the recent "Amplituhedron program for Scattering amplitudes" in which fundamental postulates of analytic S-matrix program undergo a radical change. In lecture one, we will start with some broad motivation for this program and introduce the essential conceptual ideas involved. We will devote end of lecture one and whole of lecture 2 in introducing the key technical tools which are needed to understand the construction of polytopes which underlie tree-level S-matrix of various scalar field theories and finally in lecture 3 , we will review how these ideas extend to scattering amplitudes at one loop. No prior knowledge of amplituhedron or geometry of polytopes is required.