  A spin-wave (SW) approach for hard-core bosons is presented to treat the
problem of two dimensional boson localization in a random potential. After a
short review of the method to compute 1/S-corrected observables, the case of
random on-site energy is discussed. Whereas the mean-field solution does not
display a Bose glass (BG) phase, 1/S corrections do capture BG physics. In
particular, the localization of SW excitations is discussed through the inverse
participation ratio.
