  An XY model with random phase shifts as a model for a superconducting glass
is studied in two and three dimensions by a zero temperature domain wall
renormalization group which allows one to follow the flows of both the coupling
constant and the disorder strength with increasing length scale. Weak disorder
is found to be marginal in two and probably irrelevant in three dimensions. For
strong disorder the flow is towards a non-superconducting gauge glass fixed
point in 2d and a superconducting glass in 3d. Our results are in agreement
with recent analytic theory and are inconsistent with earlier predictions of a
re-entrant transition to a disordered phase at very low temperature and with
the loss of superconductivity for any finite amount of disorder.
