Reduction of Representations of SUm+n with respect to the Subgroup SUm ⊗ SUn

A direct and rapid method is described for the reduction of representations of the special unitary group SUm+n with respect to its SUm ⊗ SUn subgroup. The technique is illustrated by specific reference to the case of SU6 and its SU2 ⊗ SU4 subgroup in the context of the recent extension of Wigner's (SU4) supermultiplet theory into the domain of particle physics. A tabulation of results is given for a slight generalization of this case where reduction is carried out with respect to U1 ⊗ SU2 ⊗ SU4.