The Topology Seminar

Spring 2009

19th May: 10:15 - 12:00, room 734, Sentralbygg II.

Liz Hanbury:  Simplicial Structures on Braid Groups and Mapping Class Groups

Abstract: The homotopy groups of spheres are notoriously hard to calculate. In this talk I will explain how simplicial methods have been used to give descriptions of the homotopy groups of S2. I will review some recent results in this area (of Jie Wu, Fred Cohen and others) and talk a little about my joint work with Jon Berrick and Jie Wu.

24th February: 10:15 - 12:00, room 656, Sentralbygg II.

Tore A. Kro (Sarpsborg):  Stratified Spaces

Abstract: We will construct certain stratified spaces inside the category of Frölicher spaces. Various ways of generalizing the notion of tangent space for a manifold will be discussed. For different purposes all of the following seem relevant: Flow spaces, curve spaces, ray spaces and continuous derivations. The differences between these will be illuminated by basic examples. We will introduce type A and type B embeddings and prove that the image of a locally compact sharp stratified space under a type B embedding into an Euclidean space naturally gets the structure of a Whitney stratified set. Furthermore, I will indicate an approach to Thom's first isotopy lemma.

Seminars given the previous Spring