Anomalous approach to the self-organized critical state in a model for ‘‘life at the edge of chaos’’

Abstract

A recently proposed model for the coevolution of biological species, known to exhibit self-organized criticality, is shown to have a dynamics which can be characterized by static critical exponents in the universality class of directed percolation. The dynamics does not exhibit the usual critical slowing down typically observed in second order phase transitions. The dynamics also modifies the critical distribution of avalanches. An exact solution for the mean field approximation of the model, along with scaling arguments and simulation results, show that these novel properties result from the use of critical fluctuations by the dynamics to drive the system to criticality.