Self-similarity of the classical $p$-adic Lie groups and Lie algebras

Abstract: We exhibit infinite lists of ramification indices $\delta$ for which the classical Lie groups over the ring of integers of $p$-adic fields admit a faithful self-similar action on a regular rooted $\delta$-ary tree in such a way that the action is transitive on the first level. These results follow from the study of virtual endomorphisms of the classical Lie lattices over the same type of rings. In order to compute the ramification indices for all the types of groups treated in the paper, we compute the indices of principal congruence subgroups of the orthogonal groups for a class of local rings.