Arbeitsgemeinschaft mit aktuellem Thema: Twisted K-Theory

Abstract

The “Arbeitsgemeinsschaft mit aktuellem Thema ‘Twisted KTheory’ ” gave an introduction to several aspects of twisted K-theory. It started with a couple of different definitions of twisted K-theory, suitable in situations of varying complexity from spaces to topological stacks. Then the AG presented tools of calculations like Chern characters with values in the corresponding twisted ordinary cohomology theories, and example calculations e.g. for Lie groups, or via T-duality. The program culminated in the theorem of Freed-Hopkins-Teleman calculating equivariant twisted K-theory of simple Lie groups in term of the Verlinde algebra of loop group representations.