Generalized Master Equation with Two Times: Diffusion in External Field
  The generalized master equation with two times, introduced in earlier, applies to the problem of diffusion in an time-dependent (in general inhomogeneous) external field. We consider the case of the quasi Fokker-Planck approximation, when the probability transition function for diffusion (PTD-function) does not possess a long tail in coordinate space and can be expanded as the function of instantaneous displacements. The more complicated case of the long tails in PTD will be discussed separately. 
S.A. Trigger