  We explore the old idea that, in a theory containing several gauge groups,
the topological defects of one gauge group coincide with those of another gauge
group. This simple 'unification' constraint has deep consequences, the best
known of which is a natural explanation of the fractional electric charge of
quarks. Here we explore the consequences of this idea for the phase diagram, in
a toy model U(1)x U(1).

High Energy Physics - Lattice