  We study the dynamics of topological defects in the triangular Ising
antiferromagnet, a related model on the square lattice equivalent to the
six-vertex ice model, and the three-state antiferromagnetic Potts model on the
square lattice. Since each of these models has a height representation in which
defects are screw dislocations, we expect them to be attracted or repelled with
an entropy-driven Coulomb force. In each case we show explicitly how this force
is felt through local fields. We measure the force numerically, both by
quenching the system to zero temperature and by measuring the motion of vortex
pairs. For the three-state Potts model, we calculate both the force and the
defect mobility, and find reasonable agreement with theory.
