Persistence in systems with conserved order parameter

Abstract

We consider the low-temperature coarsening dynamics of a one-dimensional Ising ferromagnet with conserved Kawasaki-like dynamics in the domain representation. Domains diffuse with size-dependent diffusion constant, $D(l) \propto l^γ$ with $γ= -1$. We generalize this model to arbitrary $γ$, and derive an expression for the domain density, $N(t) \sim t^{-ϕ}$ with $ϕ=1/(2-γ)$, using a scaling argument. We also investigate numerically the persistence exponent $θ$ characterizing the power-law decay of the number, $N_p(t)$, of persistent (unflipped) spins at time $t$, and find $N_{p}(t)\sim t^{-θ}$ where $θ$ depends on $γ$. We show how the results for $ϕ$ and $θ$ are related to similar calculations in diffusion-limited cluster-cluster aggregation (DLCA) where clusters with size-dependent diffusion constant diffuse through an immobile `empty' phase and aggregate irreversibly on impact. Simulations show that, while $ϕ$ is the same in both models, $θ$ is different except for $γ=0$. We also investigate models that interpolate between symmetric domain diffusion and DLCA.