RELATIVISTIC DYNAMICS OF WAVE-PACKETS FOR SPIN-1/2 PARTICLES IN AN ELECTROMAGNETIC-FIELD

Classical and quantum dynamics of wave packets for spin-1/2 particles are analysed in the presence of an electromagnetic field. An almost exact agreement is found between these two approaches, both in the strong and the weak coupling limits. The question of negative energy states is discussed, and it is shown that they are not produced in such an interaction. The divergence problem of the perturbation expansion of the particles wavefunction is discussed, the source of which is explained.