ABSTRACT
This chapter discusses the motion of a particle in a random potential and describes the general quantum kinetic equation in terms of diagrams. It introduces the Wigner function and establishes a criterion for the validity of the classical kinetic equation. This Boltzmann equation for a particle in a random potential is then used to calculate the mobility. The central object to the Boltzmann approach to non-equilibrium classical statistical mechanics is the one-particle probability distribution function on phase space. In quantum mechanics Heisenberg's uncertainty principle excludes the existence of a probability distribution with such a physical interpretation, but not, however, the introduction of a function with formal resemblance to it. The weak-disorder kinetic equation for a particle in a random potential is of course immediately obtained from classical mechanics, granted the stochastic treatment of the impurity scattering.
