The dielectric properties of the massive medium at finite density

The action method, which is applied to discuss the dielectric properties of massless medium, the QCD or QED plasma, is extended to study the dielectric function (ε) and the magnetic permeability (μ-1) of the massive nuclear matter. Taking the ωNN interaction as an example, the essential features of the physical picture of the ε and the μ-1 are investigated at the finite nucleon density. The nontrivial structures of the dielectric function are found both in the space-like and the time-like regime. Through analyzing the physical mechanisms for two kinds of induced currents in the nuclear matter, we give the explanations for these two nontrivial structures