Unitary Symmetry and Electromagnetic Interactions

The general form of the electromagnetic interaction in the octet version of the proposed "higher symmetry" scheme based on the group $S{U}_3$ is derived. The result, which is applicable to an arbitrary multiplet, is expressed in an especially simple form by introducing the notion of $U$ spin. Relations among electromagnetic form factors, mass splittings, decay amplitudes, and scattering amplitudes, previously obtained by various authors in the case of octets, are shown to follow immediately, as well as their generalizations to arbitrary multiplets. Where possible, comparisons are made with experiment.