The shell model: a growth model with a tunable fraction of forgotten growth sites

Abstract
The authors introduce and discuss a new model in which the growth sites are driven with a power law, ralpha , away from the original seed. The concept of 'forgotten' growth sites is developed. They find that the fraction of forgotten growth sites, the 'order parameter' for this problem, is zero for alpha below a critical value alpha c=1, and increases sharply for alpha > alpha c with a critical exponent beta approximately=2/3 in two dimensions.