11-07U

The Bose-Einstein condensation in the Bose-Hubbard model with two local states and the particle hopping in the excited band only is investigated. For the purpose of a consideration of the non-ergodicity the single-particle spectral density is calculated in the random phase approximation by means of the temperature boson Green functions. The non-ergodic contribution to the momentum distribution function of particles (connected with the static density fluctuations) increases significantly and becomes comparable with the ergodic one in the superfluid phase near the tricritical point.