Bounded Littlewood identities

We describe a method, based on the theory of Macdonald-Koornwinder polynomials, for proving bounded Littlewood identities. Our approach provides an alternative to Macdonald's partial fraction technique and results in first examples identities Macdonald polynomials. These identities, which take form decomposition formulas polynomials type (R,S) terms A, are q,t-analogues known branching characters symplectic, orthogonal special groups, important plane partitions. As applications our we obtain combinatorial affine Lie algebras, Rogers-Ramanujan such algebras complementing recent Griffin et al., transformation Kaneko-Macdonald-type hypergeometric series.