COARSENING ON PERCOLATION CLUSTERS - OUT-OF-EQUILIBRIUM DYNAMICS VERSUS NONLINEAR RESPONSE

We analyse the violations of linear fluctuation-dissipation theorem (F DT) in the coarsening dynamics of the antiferromagnetic Ising model on percolation clusters in two dimensions. The equilibrium magnetic resp onse is shown to be nonlinear for magnetic fields of the order of the inverse square root of the number of sites. Two extreme regimes can be identified in the thermoremanent magnetization: (i) linear response a nd out-of-equilibrium relaxation for small waiting times (ii) nonlinea r response and equilibrium relaxation for large waiting times. The fun ction X(C) characterizing the deviations from linear FDT crossovers fr om unity at short times to a finite positive value for longer times, w ith the same qualitative behaviour whatever the waiting time. We show that the coarsening dynamics on percolation clusters exhibits stronger long-term memory than usual Euclidean coarsening.