A new SU(1,1) coupling scheme, based on the discrete class representations, is proposed to construct factorizable dual amplitudes. We introduce dual vertices for off-shell particles of even spin and discuss other applications of the method. Our analysis suggests the non-existence of a dual vector current within the context of the conventional Veneziano model.

• Received 7 September 1971

DOI:https://doi.org/10.1103/PhysRevD.4.3098