Gary Morris
University of East Anglia

Title: Expansive group actions on the circle

It is well known that a single homeomorphism (defining a continuous Z-action) cannot act expansively on the circle. On the other hand, there is an expansive action of a solvable group on the circle. We show that any expansive group action has a dense set of non-trivial fixed points and deduce that Z^d cannot act expansively on the circle. Certain geometrically natural actions are studied and shown to be expansive.