  We consider a one-dimensional Hubbard model in the presence of disorder. We
compute the charge stiffness for a mesoscopic ring, as a function of the size
$L$, which is a measure of the permanent currents. We find that for finite
disorder the permanent currents of the system with repulsive interactions are
larger than those of the system with attractive interactions. This counter
intuitive result is due to the fact that local density fluctuations are reduced
in the presence of repulsive interactions.
