On the self-similarity of the norm one group of $p$-adic division algebras

Abstract

Let $p$ be a prime, $D$ a finite dimensional noncommutative division ${\mathbb{Q}}_p$-algebra, and $S{L}_1(D)$ the group of elements of $D$ of reduced norm $1$. When the center of $D$ is ${\mathbb{Q}}_p$, we prove that no open subgroup of $S{L}_1(D)$ admits self-similar actions on regular rooted trees. Moreover, we prove results on ${\mathbb{Z}}_p$-Lie lattices that allow to deal with the case where the center of $D$ is bigger than ${\mathbb{Q}}_p$, and lead to the classification of the torsion-free $p$-adic analytic pro-$p$ groups $G$ of dimension less than $p$ with the property that all the nontrivial closed subgroups of $G$ admit a self-similar action on a $p$-ary tree. As a consequence, we obtain that a nontrivial torsion-free $p$-adic analytic pro-$p$ group $G$ of dimension less than $p$ is isomorphic to the maximal pro-$p$ Galois group of a field that contains a primitive $p$-th root of unity if and only if all the nontrivial closed subgroups of $G$ admit a self-similar action on a regular rooted $p$-ary tree.

arXiv commentWith respect to v1, some results were strengthened; in particular, see Theorem A and Theorem B. There were some structural changes in the presentation