Entropy Zero $\times$ Bernoulli Processes are Closed in the $\bar d$-Metric

Abstract

An entropy zero $\times$ Bernoulli process is a stationary finite state process whose shift transformation is the direct product of an entropy zero transformation and a Bernoulli shift. We show that the class of such transformations which are ergodic is closed in the $\bar{d}$-metric. The $\bar{d}$-metric measures how closely two processes can be joined to form a third stationary process.