Critical dynamics of random-field Ising systems with conserved order parameter.

Motivated by recent experiments on critical binary fluid mixtures in porous media, the dynamics of random-field Ising systems with conserved order parameter are considered. In the one-phase regime a new dynamic crossover length l sub x is found: for q ~ q sub x the temporal decay has a strongly nonexponential component, reflecting the activated dynamics of this system. As the ordering transition is approached, this dynamic length, l sub x, diverges as l sub x ~ exp (xi sup psi), where xi is the static correlation length, and the activation free energy barriers scale as xi sup psi.