  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.
