On the random phase approximation based on the thermo field dynamics formalism

Abstract

A comparative stdy of the random phase approximation is reported in the case of the following three approches based on the thermo field dynamics formalism: (A) the Tanabe approach, (B) the Hatsuda approach and (C) the approach developed by the present authors. The basic viewpoint is to formulate the random phase approximation by picking up the quadratic terms with respect to bosons in the boson expansion theory for the thermo field dynamics formalism. It is concluded tha the approach (C) appears to be superior to the other two approaches.