Let $(X,\mathcal{X},\mu)$ be a probability measure system, $T:X\to X$ be a $\mu$-preserving isomorphism on $X$. Let $A\in \mathcal{X}$ such that $\mu(\bigcup_{n\ge 0}T^nA)=1$, and $\mu_A$ be the conditional measure of $\mu$ on $A$. For any point $x\in A$, let $n(x)=\inf\{n\ge1: T^nx\in A\}$ be the first return to $A$ (it is finite for $\mu$-a.e. $x\in A$ by Poincare recurrence theorem). Define the first-return map $T_A:A\to A$, $x\mapsto T^{n(x)}x$, which preserves $\mu_A$. It is well known that $(X,\mu,T)$ is [ergodic][1] if and only if $(A,\mu_A,T_A)$ is ergodic. It seems there is a different story for mixing properties. 1. Assume $(X,\mu,T)$ is (strongly) [mixing][2]. Is $(A,\mu_A,T_A)$ also mixing? 2. Assume $(A,\mu_A,T_A)$ is mixing. Is $(X,\mu,T)$ also mixing? If not always true, any sufficient condition or counterexample will be also great. Thanks! ------ I forgot to add an important assumption that the return-time function $n$ is **unbounded**. In particular, this assumption rules out the suspension with constant roof functions. [1]: http://en.wikipedia.org/wiki/Ergodicity [2]: http://en.wikipedia.org/wiki/Mixing_%28mathematics%29#Mixing_in_dynamical_systems