Ben Gripaios (University of Cambridge)
Title: Differential cohomology and topological actions
Abstract: In this talk, aimed at a general audience, I discuss how topological actions for quantum field theories can be both constructed and classified by a mathematical gadget known as differential cohomology and describe the intricate interplay with global and local (a.k.a. gauge) symmetries. Examples include the Aharonov-Bohm effect, the Dirac monopole, Chern-Simons terms, theta terms, and Wess-Zumino-Novikov-Witten terms (both gauged and ungauged).