Dynamical conductivity of the dilute Lorentz gas with spherically symmetric scatterers

The dynamical conductivity of the Lorentz gas with spherically symmetric po tentials is studied to lowest order in the density of scatterers. The frequ ency-dependent friction coefficient is calculated from the Fourier transfor m of the force-force time-correlation function determined by the dynamics o f a single scattering process. The corresponding dynamical conductivity var ies with frequency on the scare of the inverse collision time. As an exampl e, the conductivity is calculated for a scattering potential of the Maxwell type.