Speaker: Henrik Densing Petersen (Univ. Copenhagen)

Title: Trouble in paradise

Date/Time: December 26 (Wed.), 2012, 3:45-4:45

Room: 118 Math. Sci. Building

Abstract: It's a well-known open problem whether (vanishing of) Lp-cohomology of a countable discrete group is invariant up to measure equivalence. One approach aims to extend the proof for L2-cohomology by defining a dimension function on Lp-spaces which ideally should retain some nice properties of the von Neumann dimension in the L2 case.

In joint work with N. Monod we show that when p > 2, such a dimension function must fail at least one crucial property, already for the additive group of integers.