Reduced kinetic equations. An influence functional approach

Abstract

A scheme for obtaining reduced descriptions of multivariate kinetic equations, based on the influence functional method of Feynmann, is presented. It is applied to the case of Fokker-Planck equations, show ing the form that results for the reduced equation. The possibility of Markovian or non-Markovian reduced description is discussed. As a particular example, the reduction of the Kramers equation to the Smoluchwski equation in the limit of high friction is also discussed.