SPA Colloquium: Aleksey Cherman (UMN)

Title: New topological couplings in quantum field theory

Abstract: Many quantum field theories, including some central to our description of nature, admit topological couplings known as theta angles. Do we really understand the full set of theta angles that can appear? Our recent work shows the answer is no. I will introduce a simple example, the Cheshire theta angle, which lies beyond the standard classification. It is an example of a large new class of theta angles that we call "symmetry theta angles". The Cheshire theta angle has potentially interesting implications for particle physics, and perhaps beyond.