Speaker: Anke Pohl (ETH Zurich)

Title: A transfer operator method for Hecke triangle groups and beyond

Abstract: Given a lattice L in the group of orientation-preserving Riemannian 
isometries PSL(2,R) of the hyperbolic plane H, Selberg theory establishes a 
close relation between the geodesic length spectrum of the orbifold L\H and 
the spectrum of the Laplace-Beltrami operator on L\H. 

For the modular group and some Hecke subgroups, combinations of results from 
the last 20 years by various reseachers (most notably, by Ruelle, Mayer, 
Chang-Mayer, Lewis-Zagier, Deitmar-Hilgert) provide a deeper relation by means 
of symbolic dynamics for the geodesic flow on L\H and evolution operators 
(transfer operators) of certain densities. 

In the talk, I will report on a transfer operator method for Hecke triangle 
groups (joint work with M. Möller) and present a program towards a uniform 
generalization to a huge class of lattices in PSL(2,R).