PROJECTION TECHNIQUES IN NON-EQUILIBRIUM STATISTICAL MECHANICS .2. INTRODUCTION OF OUTSIDE FIELDS

A generalization of the projection methods developed in the previous paper, is used to obtain kinetic equations for systems in strong fields, with arbitrary time dependence. The most striking effect of these outside fields is the resulting field dependence of the collision (memory) terms in the kinetic equations. As a consequence these equations can in general not be approximated by Markoffian master equations. The precise conditions which allow such a reduction are studied as are the conditions which allow the construction of equations which are equivalent with those obtained in a linear response theory. Comparing these it is demonstrated that a linear approximation for small (but time dependent) outside fields can not be expected to be valid for arbitrary long times. © 1969.