Engel probability in wreath products of $p$-groups

Abstract

We give upper and lower bounds for the number of solutions of the equation $e_n(x,y)=g$ in the group $W_k=(C_p\wr C_{p^k}{)}^2$, where $e_n(x,y)$ is the $n$-th Engel word and $g\in W_k$. We obtain several corollaries from this. First, we prove a stronger version of the Amit-Ashurst conjecture for Engel words in $W_k$. We also prove that Engel words are not probabilistic identities in profinite groups with arbitrarily large wreath product quotients $W_k$. To conclude, we construct closed subsets of $(C_p\wr {\mathbb{Z}}_p{)}^2$ with positive Haar measure, empty-interior, and which are the preimage of an Engel word map.

19 pages