KINETICS OF DOMAIN GROWTH IN A RANDOM-FIELD MODEL IN 3 DIMENSIONS

We present the first detailed numerical study of domain growth in the ordered phase of a 3D quenched random-field (RF) model. The nonconserved order parameter obeys the time-dependent Ginzburg-Landau equations. At late times, the scaling functions of the RF and pure systems are identical, placing them in the same universality class, as defined via the renormalization group. The domain size R(t) grows initially as t1/2 and then crosses over to slow logarithmic evolution. This is interpreted as arising from a renormalization of the kinetic coefficient at short length scales and can be associated with a dangerously irrelevant operator at the zero-temperature fixed point.