Quantum and Gravitational Theory Group

September 11, 2025

Title: Entanglement Bootstrap and conformal field theory

Abstract: Theoretical physicist John McGreevy (UCSD) will introduce the Entanglement Bootstrap, a program to extract and understand the universal information characterizing a phase of matter starting from the entanglement structure of a piece of a single representative state. This universal information is usually packaged in the form of a quantum field theory; the program therefore provides a surprising new perspective on quantum field theory. McGreevy will discuss what we can learn about gapped topological phases and their associated topological field theories, and about quantum critical points and their associated conformal field theories.

September 25, 2025

Title: Particle-Soliton Degeneracy in 2D QCD from Spontaneously Broken Non-invertible Symmetry.

Abstract: Quantum chromodynamics in two spacetime dimensions admits a finite non-invertible symmetry described mathematically by a fusion category. This symmetry is spontaneously broken at long distances, leading to distinct vacua. When the theory has a mass gap, the spectrum is therefore characterized by particle excitations above a single vacuum and soliton sectors interpolating between vacua. In this talk, I will explain how to use the theory of 2D topological cosets, anyon condensation of 3D TQFTs, and the representation theory of fusion categories to obtain exact results about this spectrum, exhibiting the allowed multiplets. Often, particles and solitons are in the same representation and therefore must have equal masses. Furthermore, the fusion category symmetry frequently implies the existence of certain stable states in the spectrum. The resulting degeneracies are encoded in quiver diagrams where nodes are vacua and arrows are excited states.

October 9, 2025

October 16, 2025

October 23, 2025

October 30, 2025

November 6, 2025

November 13, 2025

November 20, 2025

December 4, 2025