Irreducible representations of tree automorphism groups into Pontryagin spaces

Abstract Let $$G=\textrm{Aut}(T)$$ G = Aut ( T ) be the automorphism group of a regular tree T . We study continuous irreducible representations of G that preserve a continuous strongly nondegenerate sesquilinear form of finite index on a Hilbert space. These are already classified for index 0 (unitary case) and for index 1. We show that there are no more representations for index $$>1$$ > 1 , which completes the classification.