ABSTRACT
This chapter clarifies the people understanding of the Boltzmann equation and the mobility. It examines the kinetic theory of an ordinary gas with electrically neutral atoms or molecules. In order to evaluate the coefficient of the thermal conductivity of the gas, it is necessary to solve the kinetic equation having a temperature gradient. The chapter examines the phenomenon of diffusion, which is the process of diluting components of gases because of their initial and non-equilibrium concentrations. The equation of motion for the electronic density matrix via the Feynman functional integral for arbitrary electron–phonon coupling constants is treated in reference and generalized to varying strong electric fields. The problem is resolved for a stationary non-linear response of band electrons to constant electric and strong electromagnetic fields.
