THERMODYNAMICS OF AN INTERACTING FERMI SYSTEM IN THE STATIC FLUCTUATION APPROXIMATION
Nigmatullin R.R., Khamzin A.A., Popov I.I.

Received: April 19, 2011

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We suggest a new method of calculation of the equilibrium correlation functions of an arbitrary order for the interacting Fermi-gas model in the framework of the static fluctuation approximation method. This method based only on a single and controllable approximation allows obtaining the so-called far-distance equations. These equations connecting the quantum states of a Fermi particle with variables of the local field operator contain all necessary information related to the calculation of the desired correlation functions and basic thermodynamic parameters of the many-body system. The basic expressions for the mean energy and heat capacity for the electron gas at low temperatures in the high-density limit were obtained. All expressions are given in the units of r_s, where r_s determines the ratio of a mean distance between electrons to the Bohr radius a₀. In these expressions, we calculate terms of the respective order r_s and r²_s. It is also shown that the static fluctuation approximation allows finding the terms related to higher orders of the decomposition with respect to the parameter r_s.