Higher order terms in the contraction of SO(3,2)
The contraction of a spin-1/2 representation of the de Sitter group SO(3,2) yields a translation operator that consists of the usual momentum operator plus a second order term, the "momentum spin" as described by F. Guersey. The contribution of momentum spin to the kinematics of a multiparticle system in a tangential space of anti de Sitter space is analyzed. It is shown that it can be described by a perturbation term with the structure of the interaction term of quantum electrodynamics. An evaluation of the corresponding coupling constant reproduces Wyler's heuristic formula for the electromagnetic coupling constant.