Approximations of contraction operators on - I
We analyze and cite applications of various, loosely related notions of uniformity inherent to the phenomenon of (multiple) recurrence in ergodic theory. An assortment of results are obtained, among them sharpenings of two theorems due to Bourgain. The first of these, which in the original guarantees existence of sets x,x+h, in subsets E of positive measure in the unit interval, with lower bounds on h depending only on m(E), is expanded to the case of arbitrary finite polynomial configurations...
A new criterion of asymptotic periodicity of Markov operators on , established in [3], is extended to the class of Markov operators on signed measures.
We study the asymptotic stability of densities for piecewise convex maps with flat bottoms or a neutral fixed point. Our main result is an improvement of Lasota and Yorke's result ([5], Theorem 4).
On explicite une conjugaison en mesure entre le décalage sur le système dynamique associé à une substitution primitive et une transformation adique sur le support d'un sous-shift de type fini, à savoir l'ensemble des chemins d'un automate dit des préfixes-suffixes. En caractérisant les préimages par la conjugaison des chemins périodiques de l'automate, on montre que cette conjugaison est injective sauf sur un ensemble dénombrable, sur lequel elle est finie-à-un. On en déduit l'existence d'une suite...
Let α be an isometric automorphism of the algebra of bounded linear operators in (p ≥ 1). Then α transforms conditional expectations into conditional expectations if and only if α is induced by a measure preserving isomorphism of [0, 1].
The notion of exact uniform rank, EUR, of an automorphism of a probability Lebesgue space is defined. It is shown that each ergodic automorphism with finite EUR is finite extension of some automorphism with rational discrete spectrum. Moreover, for automorphisms with finite EUR, the upper bounds of EUR of their factors and ergodic iterations are computed.