Abstract:

We take the Klein-Gordon equation as the fundamental wave equation for free particles. The subsidiary equations are treated only as initial conditions and a minimal interaction is defined as one which « conserves » the supplementary conditions. We find the minimal interaction with the electromagnetic field of spin s=0, 1/2 and 1, particles and show the equivalence with the usual treatment for s = 0 and 1/2. For s=l we obtain the Toung and Mills nonlinear coupling. We also find the minimal coupling for pseudo-scalar particles in interaction with nucleons. The resultant minimal theory is equivalent to the usual pseudoscalar coupling theory. © 1963 Società Italiana di Fisica.