  The meron-cluster algorithm was previously used to extensively study the
physics associated with the spontaneous breaking of a discrete symmetry. We
recently discovered that a larger class of models with spontaneous breaking of
continuous symmetries can also be simulated using the meron-cluster algorithm.
Here we study one of these new models which belongs to the attractive Hubbard
model family. In particular we study the spontaneous breaking of the U(1)
fermion number symmetry in two dimensions and find clear evidence for a
Kosterlitz-Thouless transition to a superconducting phase.
