THE ELECTROMAGNETIC COUPLING IN KEMMER-DUFFIN-PETIAU THEORY

We analyze the electromagnetic coupling in the Kemmer-Duffin-Petiau (K DP) equation. Since the KDP equation which describes spin-0 and spin-1 bosons is of Dirac type, we examine some analogies with and differenc es from the Dirac equation. The main difference with the Dirac equatio n is that the KDP equation contains redundant components. We will show that as a result certain interaction terms in the Hamilton form of th e KDP equation do not have a physical meaning and will not affect the calculation of physical observables. We point out that a second order KDP equation derived by Kemmer as an analogy to the second order Dirac equation is of limited physical applicability as (i) it belongs to a class of second order equations which can be derived from the original KDP equation and (ii) it lacks a back-transformation which would allo w one to obtain solutions of the KDP equation out of solutions of the second order equation. (C) 1998 Elsevier Science B.V.