“…The branching problem is an important problem in representation theory, algebraic combinatorics and orthogonal polynomials on root systems, see e.g., [8,9,15,16,18,19,21,22,23,24,25,26,29,31,34,35,47]. In this paper we are interested in q, t-analogues of multiplicity-free branching rules such as (1.2) and (1.4).…”