Abstract
We begin by giving a new proof of the equivalence between the Liouville property and vanishing of the drift for symmetric random walks with finite first moments on finitely generated groups; a result which was first established by Kaimanovich-Vershik and Karlsson-Ledrappier. We then proceed to prove that the product of the Poisson boundary of any countable measured group (G, μ) with any ergodic (\(\left( {G,\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{\mu } } \right)\) )-space is still ergodic, which in particular yields a new proof of weak mixing for the double Poisson boundary of (G, μ) when μ is symmetric. Finally, we characterize the failure of weak-mixing for an ergodic (G, μ)-space as the existence of a non-trivial measure-preserving isometric factor.
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Björklund, M. Random walks on countable groups. Isr. J. Math. 217, 371–382 (2017). https://doi.org/10.1007/s11856-017-1451-9
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DOI: https://doi.org/10.1007/s11856-017-1451-9