Relativistic dynamics of charges in electromagnetic fields: An eigenspinorapproach

Analytical solutions and fresh insights for the relativistic dynamics of ch arges in classical electromagnetic fields are made possible by an eigenspin or approach. The Lorentz-force equation takes a simple spinorial form when expressed in terms of an amplitude of the Lorentz transformation that descr ibes the motion of the charge in Clifford's geometric algebra of physical s pace. Algebraic projectors allow explicit analytical solutions to be found for charges in arbitrary initial motion interacting with monochromatic plan e waves, with directed planewave pulses, and with pulses superimposed on st atic axial fields. The treatment tests the classical effective mass of a dr essed charge and leads to a refinement of the concept of ponderomotive mome ntum. Implications for a pulsed autoresonance laser accelerator are briefly discus sed. [S1050-2947(99)07308-4].