TOPOLOGY SEMINAR

"Euler Characteristics And Subgroup Control

Of Homotopy"

By

AbstractIn the context of fusion theory, several categories arise that record different aspects of the p-local data of finite groups. By considering their classifying spaces, these categories can be thought of as topological objects. It is natural to ask whether the entire category is needed to obtain the classifying space, or if there is a preferred collection of subgroups where all the homotopical information is concentrated. In this talk, we will discuss this control of homotopy question, aided by Leinster's theory of Euler characteristics of EI-categories. We will review this theory and explain how it can be used to suggest which subgroups are likely to determine the homotopy type in different situations, then outline some of the proofs that control is actually achieved. .

**Date: ****Monday, November 30, 2015**

**Time: ****13.40 – 14:30**

**Place: ****Mathematics Seminar Room,
SA-141**

**All are most cordially invited.
Tea and cookies will be served after the talk.**