Logic Seminar

Slawomir SoleckiCornell University
Closed groups generated by generic measure preserving transformations

Friday, April 22, 2022 - 2:45pm
Malott 206

The behavior of a measure preserving transformation, even a generic one, is highly non-uniform. In contrast to this observation, a different picture of a very uniform behavior of the closed group generated by a generic measure preserving transformation has emerged. This picture included substantial evidence that pointed to these groups being all topologically isomorphic to a single group, namely, $L^0$---the non-locally compact, topological group of all Lebesgue measurable functions from $[0,1]$ to the circle. In fact, Glasner and Weiss asked if this was the case.

We will describe the background touched on above, including the relevant definitions. Further, we will indicate a proof of the following theorem that answers the Glasner--Weiss question in the negative: for a generic measure preserving transformation $T$, the closed group generated by $T$ is not topologically isomorphic to $L^0$. The proof rests on an analysis of unitary representations of $L^0$.