Topološki seminar Ljubljana-Zagreb

Topološki seminar Zagreb-Ljubljana se bo sestal v Ljubljani. 
Predavala bosta Eva Horvat in Blaž Jelenc.

Eva Horvat, Plumbings of 4-manifolds and their boundaries

We will define plumbings of disc bundles over orientable surfaces. These constructions may be presented by weighted graphs or Kirby diagrams; some ways of manipulating those diagrams will be discussed. Many interesting 3-manifolds arise as boundaries of plumbings. Starting with Kirby diagram of a plumbing, it is possible to calculate some numerical invariants of its boundary.

 

Blaž Jelenc, Serre fibrations in the Morita category of topological groupoids

I will present the Morita category of topological groupoids and
pointed topological groupoids. Then I will describe the classifying space of topological groupoid, the homotopy groups of topological groupoid, the generalization of the notion of Serre fibration to the Morita category of topological groupoids and the associated long exact sequence of homotopy groups. Then I will give various examples of Serre fibrations and calculations of homotopy groups of topological groupoids.