A nonideal Bose gas at finite temperatures

The present paper, based on an obvious generalization of the formalism of Belyaev [1,5], supplements the work of Belyaev [2] for the case T 0. The temperature dependence of the quasiparticle excitation and damping spectrum, the ground state energy, and the thermodynamic quantities is determined to second order in the gas-density parameter using the constant amplitude approximation. In the limiting case of free particles, the results are obtained for an ideal gas with T < T₀, where T₀ is the condensation temperature of the ideal Bose gas.In conclusion I wish to thank B. T. Geilikman, under whose supervision this work was performed.