Published online by Cambridge University Press: 02 February 2010
We introduce a functor which associates to every measure-preserving system (X,ℬ,μ,T) a topological system defined on the space of twofold couplings of μ, called the topological lens of T. We show that often the topological lens ‘magnifies’ the basic measure dynamical properties of T in terms of the corresponding topological properties of . Some of our main results are as follows: (i) T is weakly mixing if and only if is topologically transitive (if and only if it is topologically weakly mixing); (ii) T has zero entropy if and only if has zero topological entropy, and T has positive entropy if and only if has infinite topological entropy; (iii) for T a K-system, the topological lens is a P-system (i.e. it is topologically transitive and the set of periodic points is dense; such systems are also called chaotic in the sense of Devaney).