It has been shown by J. Feldman, P. Hahn and CC Moore that every non-singular action of a
second countable locally compact group has a countable (in fact so-called lacunary) …

We replace measure with category in an argument of GW Mackey to characterize closed
subgroups H of a totally nonmeager, 2nd countable topological group G in terms of the …

Contributes to the theory of Borel equivalence relations, considered up to Borel reducibility,
and measures preserving group actions considered up to orbit equivalence. This title …

In this paper we shall study extensions in the theory of ergodic actions ofa locally compact
group. If G isa locally compact group, by an ergodic G-space we mean a Lebesgue space …

It is shown that if a second countable locally compact group G acts nonsingularly on an
analytic measure space (S, μ), then there is a Borel subset E⊂ S such that EG is conull in S …

The theory of definable equivalence relations has been a very active area of research in
descriptive set theory during the last three decades. It serves as a foundation of a theory of …

The study of continuous group actions is ubiquitous in mathematics, and perhaps the most
general kinds of actions for which we can hope to prove theorems in just ZFC are those …

If a countable discrete group acts ergodically on a standard Borel space with a quasi-
invariant measure, there is a von Neumann algebra associated to it by the classical …

This paper consists essentially of the text of a series of four lectures given by the author in
the Summer Conference on General Topology and Applications, Amsterdam, August 1994 …

Classically, ergodic theory began with the study of flows or actions of R. Later, for technical
reasons, much of the theory was first developed for actions of Z. More recently, there has …