Anticausal time series
= Anticausal time series
{title2=$X_t=-\sum_{j\geq1}\phi^{-j}Z_{t+j}$}
= Anticausal
{synonym}
An anticausal noise representation uses future rather than present and past innovations. For a two-sided AR(1) equation with $|\phi|>1$, the stationary solution is $X_t=-\sum_{j\geq1}\phi^{-j}Z_{t+j}$. Thus stationary existence alone does not require causality.