Linear response, density oscillation and two-particle Green’s function of Fermion systems. - I

Edward John Leonard

Weitao Yang

A new approach for the calculation of the linear response of both the ground and thermal-equilibrium states of many-electron systems is proposed via an integral formulation of the density-functional theory. Based on the path-integral representation of the one-particle Green's function, the frequency-dependent linear-response function for the Kohn-Sham noninteracting system is expressed as an explicit functional of the Kohn-Sham local potential, instead of the summation over the single-electron orbitals. Thus the dynamic linear density response can be determined as the solution of self-consistent equations which only need as input the total electron density of the ground or the equilibrium state. Exchange and correlation effects are incorporated. Because orbitals are not employed, the formulation provides the possibility for calculations of linear-response properties, such as dynamic polarizability and photoabsorption cross sections of systems with very many electrons. The present formulation can also be applied to general fermions.

M. K. Weigel

A.S. Reiner

Using the Green's-function technique of Martin, Schwinger, and Puff, a calculation is made of the total linear response of nuclear matter, as measurable, for instance, in an inelastic electron or muon scattering experiment. In the independent-pair approximation used, two contributions stand out: the quasielastic response of properly dressed particles with well-defined lifetimes, and the contribution due to the scattering between those particles. An extensive analysis is made of the importance of the transverse component of the electromagnetic interaction as well as of the two mentioned contributions. The properly defined quasielastic scattering is predicted to dominate the scattering. A comparison is made with previous calculations by Czy\ifmmode \dot{z}\else \.{z}\fi{} and Gottfried.

Arnold J. Glick