Koornwinder’s polynomials and representations of the conformal group

Abstract

The tensor product of two massive, spinless, positive-energy ray representations of the conformal group of spacetime SO0(4,2)/Z2 is reduced in a momentum basis. The basis vectors for the irreducible subspaces (the ’’Clebsch–Gordan coefficients’’) are found to be intimately connected with Koornwinder’s polynomials in two dimensions.