Restricting holomorphic discrete series representations to a compact dual pair

The goal of this article is to study the branching problem for a holomorphic discrete series representation of the conformal group of a simple Euclidean Jordan algebra $V$ restricted to the subgroup $\operatorname{PSL}_2(\mathbb{R})\times\operatorname{Aut}(V)$ where $\operatorname{Aut}(V)$ denotes the compact group of automorphisms of $V$. We use a realization of the holomorphic discrete series on a space of vector-values $L^2$-functions as well as the stratified model developed by the second author to relate the branching problem to the decomposition of certain representations of the compact group $\operatorname{Aut}(V)$ and to vector-valued orthogonal polynomials.