Electrodynamics of direct interparticle action. II. Relativistic treatment of radiative processes

This paper is a sequel to an earlier paper that described nonrelativistic quantum electrodynamics in terms of the time symmetric theory of direct interparticle action. The restriction to a nonrelativistic treatment is removed in the present paper. The path integral approach to quantum mechanics is extended to include relativistic particles with spin as a preliminary to achieving this end. The response of the Universe can be obtained in two ways, by an extension of the method of the previous paper or by using a general condition analogous to the general condition, &#931;<SUB>particles</SUB>[F<SUB>ret</SUB>&#8722;F<SUB>adv</SUB>]=0, of Wheeler and Feynman. The second method is used in the present paper since it avoids the need to calculate the detailed properties of the absorber. The rules of quantum electrodynamics in the form stated by Feynman are derived, thereby showing that all the practical results of the usual theory of quantum electrodynamics can also be obtained from the direct particle theory. Radiation corrections are discussed. The direct particle theory throws some light on the processes of renormalization. The point of view that both mass and charge should be finite before as well as after renormalization is partially developed