  This paper analyzes, for a multi-particle system of spin-1/2 particles, the
consequences of replacing the Poincare group as fundamental symmetry group by
the de Sitter group SO(3,2). The flat-space approximation of the de Sitter
group by the Poincare group defines a superselection rule, which correlates
spin and momentum of particles. This correlation can be formulated as an
interaction between two particles, which exhibits properties of the
electromagnetic interaction.
