AVALANCHES AND CORRELATIONS IN DRIVEN INTERFACE DEPINNING

We study the critical behavior of a driven interface in a medium with random pinning forces by analyzing spatial and temporal correlations i n a lattice model recently proposed by Sneppen [Phys. Rev. Lett. 69, 3 539 (1992)]. The static and dynamic behavior of the model is related t o the properties of directed percolation. We show that, due to the int erplay of local and global growth rules, the usual method of dynamical scaling has to be modified. We separate the local from the global par t of the dynamics by defining a train of causal growth events, or ''av alanche,'' which can be ascribed a well-defined dynamical exponent z(l oc) = 1 + zeta(c) congruent-to 1.63, where zeta(c) is the roughness ex ponent of the interface.