Week 30.09.2024 – 06.10.2024

How are bulk strings related to boundary Feynman diagrams? I will give an overview of my work with Rajesh Gopakumar on deriving the closed string dual to the simplest possible gauge theory, a Hermitian matrix integral. Working in the conventional 't Hooft limit, we extract topological string theories which replace the minimal string away from the double-scaling limit. We show how to exactly reconstruct both the closed string worldsheet and its embedding into the emergent target space, purely from the matrix Feynman diagrams. I'll close by embedding our results in the broader context of AdS/CFT.

Coset symmetry arises in many systems such as Higgs phases of gauge theories and quantum spin liquids. When the coset is quotient by a non-normal subgroup, coset symmetry becomes a non-invertible symmetry. I will discuss properties of coset non-invertible symmetry and its fractionalization using examples in field theories and lattice models, and comment on the dynamical implication. The talk is based on arXiv: 2405.20401 and work in progress with Ryohei Kobayashi and Carolyn Zhang

SymTFTs (or, relatedly, the sandwich construction) have emerged recently as a useful way to think of categorical symmetries. I will give a brief description of this construction, and then review recent work on how to obtain the SymTFT data from geometry in the context of geometric engineering.

Recent developments in the field of integrability include the discovery of higher-dimensional generalised Chern-Simons theories. These theories encode a linear system known as a Lax pair which underpins the integrability of the lower-dimensional theory. We will start with a generous review of these developments before presenting some extensions of this formalism. The applications of these extensions include: integrable deformations (a class of less-symmetric string backgrounds which are nonetheless integrable), stationary axisymmetric general relativity, and gauged WZW models.