A Chung-Fuchs type theorem for skew product dynamical systems

Abstract

We prove a Chung-Fuchs type theorem for skew product dynamical systems such that for a measurable function on such a system, if its Birkhoff average converges to zero almost surely, and on typical fibres its Birkhoff sums have a non-trivial independent structure, then its associated generalised random walk oscillates, that is the supremum of the random walk equals to $+\infty$ and the infimum equals to $-\infty$.