Use of the two-time temperature formalism to study quasi-particle excitation in a Fermi system with a Coulomb interaction.

The method of two-time temperature Green's functions is used to study a system with a Coulomb interaction. The decoupling procedure leads to an equation for the mass operator and a single-particle Green's function. This Green's function is used to obtain the single-particle excitation spectrum of the system and the thermodynamic potential for high and low temperatures.