The spectral localizer for semifinite spectral triples

Abstract

The notion of spectral localizer is extended to pairings with semifinite spectral triples. By a spectral flow argument, any semifinite index pairing is shown to be equal to the signature of the spectral localizer. As an application, a formula for the weak invariants of topological insulators is derived. This provides a new approach to their numerical evaluation.

numerous improvements taking into account comments by the referees, to appear in Proc. AMS