Spreading phenomena in which growth sites have a distribution of lifetimes

Originally, studies of the growth of fractal objects such as percolation clusters assumed that the growth sites have an infinite lifetime. Recently Bunde, Miyazima and Stanley (1986) have studied the effect of a fixed finite lifetime and they have found that the long-time growth evolves towards the kinetic growth walk with self-avoiding walk critical exponents. Here the authors consider for two dimensions the general case in which each growth site is randomly assigned infinite lifetime (with probability q) or a finite lifetime (with probability q) or a finite lifetime (with probability 1-q). The phase diagram is similar to that of site-bond percolation, a model used to describe solvent effects in gelation.