Dielectric formulation of strongly coupled electron liquid at metallic densities: Longitudinal response

The longitudinal dielectric response function for a strongly coupled plasma is formulated in such a way that it satisfies a set of physical requirements representing strong-coupling effects, namely, the equation of continuity, long-time relaxational behavior, static and dynamic local-field corrections, and the frequency-moment sum rules. Dynamic effects arising from Coulomb collisions are considered in terms of the long-time relaxation rate and the multipair excitation spectrum; explicit expressions for these quantities are obtained as functionals of the static form factor. The theory provides a quantitative description of the long-wavelength excitations, such as the plasmons, the single-pair and multipair excitations, in a way consistent with the known qualitative features.