Calculation of dynamic critical properties from a cluster-reaction theory

Critical fluctuations in kinetic Ising models are interpreted in terms of cluster reactions. The basic assumption, that clusters with $l$ spins grow at a rate $\propto l^r$, is tested by Monte Carlo computations in the single-spin-flip case. The dynamic susceptibilities associated with order parameter and energy are then calculated also for nonzero magnetic field, and are shown to fulfill dynamic scaling. The exponent $\mathrm{}(2-r)\mathrm{}\beta \delta$ of the relaxation times can be different from the susceptibility exponent $\gamma$.