zeta-function regularization and the interacting Bose gas at low   temperature
  zeta-function methods are used to study the properties of the non-relativistic interacting Bose gas at finite temperature and density. Results for the ground state energy and pressure are obtained at both zero and finite temperature. The method used does not restrict the form of the interaction, which can be completely general. A similar procedure is then applied to evaluate the ground state energy of a binary mixture consisting of different bosons. Analytical results are obtained in the case where the two species have the same mass. 
David J. Toms