Zoom link.

https://msri.zoom.us/s/585445592

This talk will consist of two parts, both describing topological invariants arising from 4D TFTs. The first part concerns higher Dijkgraaf-Witten theory based on a finite n-group. After reviewing the construction we will look at the resulting invariants of 4-manifolds and of knotted surfaces, with a particular focus on the finite 2-group case. The second part will cover BF theory and its connection to Reidemeister torsion.

Notes 498 KB application/pdf

Torsion And Homotopical Invariants From 4D TFTs