  We study a one-dimensional disordered quantum fluid with linearly confining
interactions (disordered Schwinger model) using bosonization and the
nonperturbative functional renormalization group. We find that the long-range
interactions make the Anderson insulator (or, for bosons, the Bose-glass) fixed
point (corresponding to a compressible state with a gapless optical
conductivity) unstable, even if the latter may control the flow at intermediate
energy scales. The stable fixed point describes an incompressible ground state
with a gapped optical conductivity similar to a Mott insulator. These results
disagree with the Gaussian variational method that predicts a Mott glass,
namely a state with vanishing compressibility but a gapless optical
conductivity.
