MS Seminar (Mathematics - String Theory)

Speaker: Nikolas Kuhn (University of Oslo)
Title: Spin structures on quadratic complexes
Date (JST): Tue, Apr 23, 2024, 13:30 - 15:00
Place: Seminar Room A
Abstract: We present a notion of spin structure for a perfect complex E (on a complex variety X) which is equipped with an oriented quadratic structure. The existence of a spin structure on E is obstructed by a natural Z/2Z-gerbe over X, carrying a universal spin structure. As an application we show how to construct a twisted virtual structure sheaf on moduli spaces of sheaves on Calabi-Yau fourfolds, which lives on the spin gerbe over a moduli space M. We expect that - after inverting 2 in the cofficients - this defines a natural class in the K-theory of M, recovering the one defined by Oh-Thomas.