Dynamical structure factor of dustry plasmas including collisions

Abstract

Recently, the study of low frequency modes in dusty plasmas has attracted much attention. Because of the high charge of the macro-particles, interaction effects play a dominant role, leading to a solid-like state with long range order. Under these conditions, dust lattice waves (DLW) are expected to occur as excitations of the ordered crystal-like structure. This is a striking phenomenon due to the fact, that the plasma was found in a solid-like state, the dispersion relation of the collective excitation on the other hand was fitted by an approximation suitable for a weakly coupled plasma. There are several theoretical approaches improving the dispersion relation. These are based on generalized hydrodynamics, the quasi-localized charge approximation or the concept of static local field corrections. While a great deal of attention is paid to static correlations, collisions are introduced by very simple arguments such as the relaxation time approximation neglecting any further frequency dependence. This chapter focuses on the dust dynamic structure factor. It presents a systematic microscopic approach based on a generalized linear response theory. Within this approach, the structure factor is given as a ratio of frequency- and momentum-dependent correlation functions allowing describing collisions beyond the relaxation time approximation.