## 3-Manifold Seminar: Bass-Serre theory

Seminar | October 16 | 2:10-3:30 p.m. | 939 Evans Hall

Nic Brody, UC BERKELEY

Department of Mathematics

Bass-Serre theory studies groups acting on trees. The action of a group on a tree determines a quotient "graph of groups", from which one can reconstruct the original group via amalgamated free products and HNN extensions. We will study the tree associated to $PSL(2,{\mathbb Q}_p)$ in detail, discuss various higher-dimensional generalizations, and describe some applications to the study of incompressible surfaces in 3-manifolds.

events@math.berkeley.edu