Representation rings for fusion systems and dimension functions

Abstract

We define the representation ring of a saturated fusion system F as the Grothendieck ring of the semiring of F-stable representations, and study the dimension functions of F-stable representations using the transfer map induced by the characteristic idempotent of F. We find a list of conditions for an F-stable super class function to be realized as the dimension function of an F-stable virtual representation. We also give an application of our results to constructions of finite group actions on homotopy spheres.