A Diagrammatic Interpretation of the Boltzmann Equation

Abstract

We study nonlinear response in weakly coupled nonequilibrium ${\varphi }^4$ theory in the context of both classical transport theory and real time quantum field theory, based on a generalized Kubo formula which we derive. A novel connection between these two approaches is established which provides a diagrammatic interpretation of the Boltzmann equation.

Comments: 5 pages in RevTex with 4 Postscript figures