IN AN ISING-MODEL WITH SPIN-EXCHANGE DYNAMICS DAMAGE ALWAYS SPREADS

We investigate the spreading of damage in Ising models with Kawasaki s pin-exchange dynamics which conserves the magnetization. We first modi fy a recent master equation approach to account for dynamic rules invo lving more than a single site. We then derive an effective-field theor y for damage spreading in Ising models with Kawasaki spin-exchange dyn amics and solve it for a two-dimensional model on a honeycomb lattice. In contrast to the cases of Glauber or heat-bath dynamics, we find th at the damage always spreads and never heals. In the long-time limit t he average Hamming distance approaches that of two uncorrelated system s. These results are verified by Monte Carlo simulations.