Some spectral computations of random walk operators (GGTSeminar)

Date:
30.04.2013
 Speaker:

Time:
15:45  16:45 Uhr

I will start by reminiding what are random walk operators on discrete group, and what are their "spectral properties". In particular we will see how are socalled NovikovShubin invariants defined, and what are the possible "types" of spectral measures. The aim of the talk will be to describe two joint results with B. Virag  1) NovikovShubin invariants don't have to be positive, contrary to a conjecture of J. Lott and W. Lueck. 2) It can happen that for a given group two random walk operators (defined for different generating sets) have different spectral measure types (i.e. one is purepoint, the other is singular continuous.) In particular I'll try to explain why both results follow from computations done by mathematical physicists.
Łukasz Grabowski, University of Oxford

Place:
Raum 1C01
im Allianzgebäude (05.20)