Relativistic composite systems and minimal coupling

Abstract

The problem of minimal coupling of relativistic composite systems having internal degrees of freedom is investigated. The ambiguity in the introduction of various internal coordinates with the same mass spectrum can be solved by probing the system with external electromagnetic interactions. For the generalized Majorana equation this procedure shows that the charged constituent of the system performs a two-dimensional Kepler motion in the Klein-Gordon approximation and not an oscillator motion.