Event time:

Thursday, April 17, 2008 - 12:30pm to Wednesday, April 16, 2008 - 8:00pm

Location:

431 DL

Speaker:

Jason Behrstock

Speaker affiliation:

Barnard/Columbia

Event description:

We will discuss a new quasi-isometry invariant of metric

spaces which we call thickness. We show that any thick metric space is

not (strongly) relatively hyperbolic with respect to any non-trivial

collection of subsets. The class of thick groups includes many

important examples such as mapping class groups of all surfaces

(except those few that are virtually free), the outer automorphism

group of the free group on at least 3 generators, fundamental groups

of graph manifolds, $SL(n,{\bf Z})$ with $n>2$, and others. We shall also

discuss some ways in which thick groups behave rigidly under

quasi-isometries. This work is joint with Cornelia Drutu and Lee

Mosher.