Structural properties of the canonical U(3) Racah functions and the U(3) : U(2) projective functions

Abstract
The class of U(3) Racah functions which are identically zero are determined from the canonical splitting of the multiplicity. These results imply the form of a special class of (projective) tensor operators. The function Gq associated with the ’’stretched’’ (maximal null space) Wigner operator is generalized and shown to be applicable in determining the denominator for the minimal null space operator.