Two-Point Function Reduction of Four-Point Amputated Functions and Transformations in and RA Basis in a Real-Time Finite Temperature NJL Model**The project partly supported by National Natural Science Foundation of China and by Grant No. LWTZ-1298 of the Chinese Academy of Sciences

Abstract

Based on a general analysis of Green functions in the real-time thermal field theory, we have proven that the four-point amputated functions in an NJL model in the fermion bubble diagram approximation behave like usual two-point functions. We expound the thermal transformations of the matrix propagators for a scalar bound state in the basis and in the RA basis respectively. The resulting physical causal, advanced and retarded propagators are respectively identical to corresponding ones derived in the imaginary-time formalism, and this shows once again the complete equivalence of the two formalisms of thermal field theory on the discussed problem in the NJL model.