Nonlocal Properties of Stable Particles

Some physical implications of the position operators studied in an earlier paper are presented. Lower limits on the dimensions, perpendicular to the momentum, of spinning particles are obtained and the partial localization of massless particles by the center-of-mass operator is discussed. The lowest order correction to a local potential, from a potential which is spherically symmetric in terms of the nonlocal center of mass, is shown to be exactly the Thomas spin-orbit coupling interaction.