ABSTRACT
The behavior of the electron liquid in the limit of very high densities is simple because here the Coulomb interaction represents a relatively small perturbation; the average potential energy is small compared to the kinetic energy. Theory of the electron liquid at metallic densities will perforce be a theory of the second category mentioned above, one whose accuracy cannot be determined with precision. This chapter aims to a consideration of the electron liquid in both the high-density and the intermediate-density regime. It develops the "equation-of-motion" method in order to consider the random phase approximation (RPA), and its possible generalizations, as part of a hierarchy of successive approximations to the electron liquid. The chapter presents a description of the electron liquid in which only the lowest-order effects of particle interaction are taken into account. Further insight into the microscopic behavior of the electron liquid, as calculated in the Hartree-Fock approximation (HFA), is obtained by considering the static pair correlation function.
