1:15-2:15 Isoperimetric inequalities of Groups and Isoperimetric Profiles of surfaces - Panos Papazoglou

It is an interesting question whether Gromov's `gap theorem' between a sub-quadratic and a linear isoperimetric inequality can be generalized in higher dimensions. There is some evidence (and a conjecture) that this might be the case for CAT(0) groups. In this talk I will explain how the gap theorem relates to past work of Hersch and Young-Yau on Cheeger constants of surfaces and of Lipton-Tarjan on planar graphs. I will present some related problems in curvature-free geometry and will use these ideas to give an example of a surface with discontinuous isoperimetric profile answering a question of Nardulli-Pansu. (joint work with E. Swenson).

2:30-3:30 Title tba - Laura Ciobanu

Abstract tba

3:30-4:15 Tea/coffee

4:15-5:15 CAT(0) groups need not be biautomatic - Ian Leary

Ashot Minasyan and I construct (or should that be find?) examples of groups that establish the result in the title. These groups also fail to have Wise's property: they contain a pair of elements no powers of which generate either a free subgroup or a free abelian subgroup. I will discuss these groups.