On the relativistic dynamics of polarized systems. II

Abstract

The classical equations of motion for electric and magnetic dipole atoms (or molecules) in an external electromagnetic field of force, derived in a previous paper on the basis of Møller's theory of the relativistic dynamics of systems with an internal angular momentum, are simplified by showing that certain terms, which contain an unphysical trembling motion (“Zitterbewegung”), are completely negligible with respect to the other terms in these equations. The resulting equations are used in order to derive the relativistic atomic energy-momentum tensor for a system, consisting of these dipole atoms. The field part of this tensor has exactly the same form as obtained before, but the material part is slightly different as a consequence of the simplification in the equations of motion. The same symmetrization procedure, as used in the preceding paper, can be applied to the total energy-momentum tensor. Radiative effects are neglected throughout the theory.