Operator algebra seminar

Speaker: Eric Reckwerdt (IMPAN)

Title: Relatively hyperbolic groups and weak amenability.

Abstract: A graph X is relatively hyperbolic to a subgraph Y if, after 'hyperbolizing' Y in a suitable sense, the resultant graph X' is hyperbolic.  Similarly, a group G is relatively hyperbolic to a subgroup P if the Cayley graph of G can be hyperbolized relative to the cosets of P.  There are a few ways to approach this process, but none yield a bounded valence graph which G acts upon.  Unfortunately, the proof that hyperbolic groups are weakly amenable requires such a bounded valence graph.  In this talk we will show how to circumvent such issues if the subgroup P is of polynomial growth.  This is joint work with Erik Guentner and Romain Tessera.