Voter Model — Interface Coarsening

Opinion dynamics in 2D: domains grow as t^(1/2) via diffusive coarsening

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In the voter model, each site copies the opinion of a random neighbor. In 2D the system coarsens as domain walls undergo random walks and annihilate — the density of interfaces decays as ρ ~ 1/ln(t). Small noise prevents full consensus, sustaining a dynamical steady state.