Lorentz covariance and the physical states in dual-resonance models

The properties of physical states in dual-resonance models under rotations in the little group of the resonance momentum are studied. It is shown how at a critical number of space-time dimensions this group can be represented just on the space of 'transverse' states constructed by del Giudice, di Vecchia and Fubini (because these are then essentially the only states which couple). Further, the action of rotations in this group on the 'photon' operators A/sup i//sub n/ is used to produce, for any number of dimensions, enough operators to create all the physical states both in the conventional model and in the model of Neveu and Schwarz. (10 refs).