Sum rules and dynamical correlations in a classical one-component plasma

Abstract

Expressions for the fourth-frequency-moment sum rule for the longitudinal and the transverse current-correlation function are obtained in the form which can be easily computed for all momentum transfers. This is made possible by carrying out analytically three of the four angular integrations involved in the three-body contribution to these moments. Numerical results for the moments are presented for some values of the plasma parameter of interest. These results are used to interpret the recent molecular-dynamics data on the dynamical structure factor using the Mori formalism. It is found that a renormalized free-particle memory function provides an overall good description of molecular-dynamics results for the dynamical structure factor over entire range of plasma parameter.