Abstract
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.
| Original language | English |
|---|---|
| Journal | Mathematical Research Letters |
| Volume | 19 |
| Issue number | 3 |
| Pages (from-to) | 525-535 |
| ISSN | 1073-2780 |
| Publication status | Published - 2012 |