Workshop
Higher structures on the unitary group and the invariants of time-reversal symmetric topological insulators
- Krzysztof Gawedzki (École Normale Supérieure de Lyon)
Abstract
I shall describe a geometric structure (a gerbe with connection) on the group U(N) that encodes the ambiguities of taking the logarithm of a unitary matrix. Such a structure, with an additional refinement, will be used to construct torsion invariants of time-reversal symmetric insulators.