Week 23.10.2023 – 29.10.2023

In these lectures we will provide a basic introduction to Supergravity as it arises in String Theory and M-Theory. We will start by introducing vielbeins and spin connections in order to construct supergravity actions. In the second lecture we will briefly introduce the maximal supergravity theories in ten and eleven-dimensions. We will briefly discuss special holonomy manifolds, explicitly construct BPS p-brane solutions and prove their non-perturbative stability. Time permitting we will discuss toroidal compactifications and U-duality. I will assume basic MSc level material (Riemannian geometry, fermions and rigid supersymmetry). The lecture notes that will be provided are largely self-contained but the text book “Supergravity” by Freedman and van Proeyen contains more details. This time, there will be two lectures (one in the morning and one in the afternoon), with pizza lunch in between them.

We will discuss how amplitudes can be used to efficiently derive classical gravitational-wave observables characterizing black hole binary encounters. This technique is very flexible and can be applied to General Relativity, but also to its extensions and, in the spirit of Effective Field Theory, can be used to describe compact objects beyond Schwarzschild black holes. We will briefly discuss some recent applications to spinning black holes and to the subleading Post-Minkowsian waveforms.

In this talk I will review recent results co-authored with Stefano Negro, Fabio Sailis and István Szécsényi. In this project we have addressed the problem of how to compute correlation functions in integrable quantum field theories perturbed by irrelevant perturbations such as the operator TTbar. It has been known for some time that integrability is preserved under such perturbations even though the S-matrix is modified by a CDD factor. Therefore, it is natural to expect that matrix elements of local fields may be computed by employing the standard form factor program, which was developed for integrable quantum field theories in the 70s. By doing so we have found that the form factors of local and semi-local fields have a universal structure which we have identified. This gives rise to correlation functions with distinct convergence/divergence properties, depending on the sign of the perturbation. In the convergent regime we find that the correlation functions scale as power-laws at short distances, similar to standard integrable quantum field theories, but with powers that are no longer the conformal dimensions of some field. At the heart of our construction is a function called the minimal form factor, whose structure I will discuss in some detail.

In this talk we will attempt to reconcile two different results on two-dimensional pure Yang-Mills theory. Specifically, we will discuss how the fact that 2d pure Yang-Mills is equivalent to a disjoint union of theories, is related to the Gross-Taylor description of 2d pure Yang-Mills as the target-space field theory of a string theory. The Gross-Taylor picture can be understood by first rewriting the Yang-Mills partition function (in a large N limit) as a sum of correlation functions in Dijkgraaf-Witten theories for the symmetric group S_n, and then interpreting those Dijkgraaf-Witten correlation functions in terms of branched covers, which leads to the string theory description. We first observe that the decomposition of the pure Yang-Mills aligns perfectly with decomposition of S_n Dijkgraaf-Witten theory, and then discuss decomposition and the branched covers interpretation. We encounter two puzzles, and to solve them, propose that the Gross-Taylor string theory has a higher-form symmetry.