  The superfluid to insulator quantum phase transition of a three-dimensional
particle-hole symmetric system of disordered bosons is studied. To this end, a
site-diluted quantum rotor Hamiltonian is mapped onto a classical
(3+1)-dimensional XY model with columnar disorder and analyzed by means of
large-scale Monte Carlo simulations. The superfluid-Mott insulator transition
of the clean, undiluted system is in the 4D XY universality class and shows
mean-field critical behavior with logarithmic corrections. The clean
correlation length exponent $\nu = 1/2$ violates the Harris criterion,
indicating that disorder must be a relevant perturbation. For nonzero dilutions
below the lattice percolation threshold of $p_c = 0.688392$, our simulations
yield conventional power-law critical behavior with dilution-independent
critical exponents $z=1.67(6)$, $\nu = 0.90(5)$, $\beta/\nu = 1.09(3)$, and
$\gamma/\nu = 2.50(3)$. The critical behavior of the transition across the
lattice percolation threshold is controlled by the classical percolation
exponents. Our results are discussed in the context of a classification of
disordered quantum phase transitions, as well as experiments in superfluids,
superconductors and magnetic systems.
