Presented by: 
Professor Greg Hjorth (UCLA/Melbourne):
Mon 2 Aug, 2:00 pm - 3:00 pm
N202 in Hawken (50)

For G a countable group, a unitary representation of G is a homomorphism from G to the group of isometries of some Hilbert space. It is natural to consider two such representations to be equivalent if they are conjugate under some isomorphism of the Hilbert space.

I will discuss recent work in descriptive set theory on the equivalence of unitary group representations, and attempt to trace those problems back to the foundational work of G. W. Mackey in the middle of last century on the issues related to infinite dimensional unitary representations.