Stretched and non-stretched exponential relaxation in Ising ferromagnets

The decay of the Hamming distance in Monte Carlo simulations of Ising models with model A dynamics is shown to be numerically efficient to investigate the dynamics also below Tc. We observe a simple exponential decay in three and four dimensions below and above the Curie temperature. In two dimensions, a stretched exponential decay is observed only below Tc. The exponent in the latter is between the two predictions of Takanao et al. and Huse and Fisher, but the dynamics of single droplets is clearly found to disagree with Takano et al.