Note on the Generating Function of Two-Time Green Functions

Abstract

A new approach to the two-time Green function method is proposed. In order to give a systematic way of decoupling the two-time Green functions and to overcome the difficulties often encountered in terminating the hierarchy of Green functions, a generating function is introduced and its properties are examined in detail for a simple model. It is shown that the generating function provides poweful tool even in the case where conventional approximation for Green functions does not work. An example of the generating function is constructed for Fermion system with two-body interaction.