  We present a Monte Carlo study of the Bose-glass to superfluid transition in
the three-dimensional Bose-Hubbard model. Simulations are performed on the
classical (3 + 1) dimensional link-current representation using the geometrical
worm algorithm. Finite-size scaling analysis (on lattices as large as
16x16x16x512 sites) of the superfluid stiffness and the compressibility is
consistent with a value of the dynamical critical exponent z = 3, in agreement
with existing scaling and renormalization group arguments that z = d. We find
also a value of $\nu = 0.70(12)$ for the correlation length exponent,
satisfying the relation $\nu >= 2/d$. However, a detailed study of the
correlation functions, C(r, tau), at the quantum critical point are not
consistent with this value of z. We speculate that this discrepancy could be
due to the fact that the correlation functions have not reached their true
asymptotic behavior because of the relatively small spatial extent of the
lattices used in the present study.
