Explicitly Covariant Algebraic Representations for Transitional Currents of Spin-1/2 Particles

Abstract

In non-relativistic quantum mechanics and in relativistic quantum theory, there exist explicitly covariant algebraic representations for transitional currents of massive spin-1/2 particles. We show that in the massless case such representations exist only for transitional currents which are non-diagonal in helicity. The diagonal currents have algebraic representations which are not explicitly covariant.