title: Critical and near-critical branching processes.
abstract: Scale-free dynamics in physical and biological systems can arise from a variety of causes. Here, we explore a branching process which leads to such dynamics. We find conditions for the appearance of power laws and study quantitatively what happens to these power laws when such conditions are violated. From a branching process model, we predict the behavior of two systems which seem to exhibit near scale-free behavior--rank-frequency distributions of number of subtaxa in biology, and abundance distributions of genotypes in an artificial life system. In the light of these, we discuss distributions of avalanche sizes in the Bak-Tang-Wiesenfeld sandpile model.
authors.affiliation: Digital Life Laboratory 136-93, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Christoph
authors.initials: C
authors.lastname: Adami
authors.forename: Johan
authors.initials: J
authors.lastname: Chu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D055592:Biophysical Phenomena; D001703:Biophysics; D005580:Fossils; D005838:Genotype; D008386:Marine Biology; D008954:Models, Biological; D009154:Mutation