Multiple ergodic theorems for arithmetic sets

Nikos Frantzikinakis, Bernard Host

Published 2015-03-24Version 1

We establish results with an arithmetic flavor that generalize the polynomial multidimensional Szemer\'edi theorem and related multiple recurrence and convergence results in ergodic theory. For instance, we show that in all these statements we can restrict the implicit parameter $n$ to those integers that have an even number of distinct prime factors, or satisfy any other congruence condition. In order to obtain these refinements we study the limiting behavior of some closely related multiple ergodic averages with weights given by appropriately chosen multiplicative functions. These averages are then analysed using a recent structural result for bounded multiplicative functions proved by the authors.