Dirac Equation Path Integral: Interpreting the Grassmann Variables (*)(**)

S u m m a r y . A functional integral for a particle obeying the Dirac equation is presented. In earlier work (reviewed here) we showed that 1) such a particle could be described as a massless particle randomly flipping direction and helicity at a complex rate i/m and 2) its between-flips propagation could be written as a sum over paths for a Grassmann variable valued stochastic process. We here extend the earlier work by providing a geometrical interpretation of the Grassmann variables as forms on SU(2). With this interpretation we clarify the supersymmetric correspondence relating products of Grassmann variables to spatial coordinates.