Mathematical Research Letters
Volume 19 (2012)
The conjugacy relation on unitary representations
Pages: 525 – 535
In a 1965 paper, E.G. Effros asked the question if the conjugacy relation for unitary representations of a locally compact second countable group is a Borel equivalence relation. In this paper, we answer this question affirmatively. This also settles a recent question raised by A.S. Kechris regarding the hierarchy complexity of unitary equivalence of probability measure preserving actions of countable discrete groups.
2010 Mathematics Subject Classification
03E15, 03E75, 22D10, 22D25, 46Lxx