DISORDERED BOSONS - CONDENSATE AND EXCITATIONS

The disordered Bose-Hubbard model is studied numerically within the Bo goliubov approximation. First, the spatially varying condensate wave f unction in the presence of disorder is found by solving a nonlinear Sc hrodinger equation. Using the Bogoliubov approximation to find the exc itations above this condensate, we calculate the condensate fraction, superfluid density, and density of states for a two-dimensional disord ered system. These results are compared with experiments done with He- 4 adsorbed in porous media.