Remanent Magnetization Decay at the Spin-Glass Critical Point: A New Dynamic Critical Exponent for Nonequilibrium Autocorrelations.

A quench of a d-dimensional spin system from a random initial configuration, { -> over S sub i (O))}, to a critical point is considered. The decay with time t of the autocorrelation with the initial condition is q sub o (t) = -> S sub i (O) (O) .-> S sub i (t) > ~ t sup (lambda sub c /Z). Naively, lambda sub c = d, but I find lambda sub c d in simulations of the pure Ising models in d = 2 and d = 3 and the += J Ising spin glass in d = 3. This suggests that lambda sub c is a new critical exponent for nonequilibrium dynamics. For a spin glass the decay of q sub o (t) is the same as that of the remanent magnetization, and thus experimentally observable.