"Geometry and Analysis on Groups" Research Seminar

Time: , 15:00–17:00
Location: Seminarraum 9, Oskar-Morgenstern-Platz 1, 2.Stock
Title: Groups acting on trees
Speaker: Alexandre Martin
Introductory part: basics of groups acting on trees, and Bass-Serre just in the case of amalgamated products: construction of the group in term of cosets, and reconstruction of the group out of the action. Main example: pi_1 of the genus 2 surface as an amalgamation of free groups (van Kampen).
"Abstract": how to use the action on the tree to understand the structure of the group: torsionfree-ness, existence of free subgroups and nonsimplicity.