Gauge-invariant wave equations for massless fields with fixed, but arbitrary, integer spin have been constructed. Extended to include interactions with external sources, the theory remains self-consistent and unitary to lowest order in the coupling. Fields describing states of one or two singletons, with the attendant interesting gauge problems, are studied. An intertwining operator is constructed that explicitly expresses the bilocal two-singleton field in terms of one-particle massless fields.

• Received 20 October 1978

DOI:https://doi.org/10.1103/PhysRevD.20.848