Title: Quasi-disjointness

Speaker: Joel Moreira (Northwestern University)

Abstract: The Kronecker factor of a measure preserving system is the factor generated by all the almost periodic functions and has an explicit algebraic description. A surprising result of Berg essentially classifies the joinings of two ergodic measure preserving ℤZ-systems in terms of the joinings of their Kronecker factors (which have an easy algebraic description), if one of the systems is (measurable) distal. Using Berg’s terminology, he showed that any ergodic ℤZ-system is *quasidisjoint*. from any ergodic distal ℤZ-system. In this talk I will explore the notion of quasidisjointness, and present an alternative definition of quasidisjointness which makes sense for measure preserving actions of any group and agrees with Berg’s definition for ℤZ actions.