RELATIVISTIC QUANTUM-MECHANICS OF BOSONS

We show that it is possible to use the Klein-Gordon, Proca and Maxwell formulations to construct multi-component relativistic configuration space wavefunctions of spin-0 and spin-1 bosons in an external field. These wavefunctions satisfy the first-order Kemmer-Duffin equation. Th e crucial ingredient is the use of the future-causal normal n(mu) (n(m u)n(mu)=1, n0 > 0) to the space-like hypersurfaces foliating space-tim e, inherent in the concept of a relativistic wavefunction, to construc t a conserved future-causal probability current four-vector from the s econd-rank energy-momentum tensor, following Holland's prescription. T he existence of a Hermitian position operator, localized solutions, co mpatibility with the second quantized thories and the question of inte rpretation are discussed.