Circuits, Attractors and Reachability in Mixed-K Kauffman Networks

Abstract

The growth in number and nature of dynamical attractors in Kauffman NK network models are still not well understood properties of these important random boolean networks. Structural circuits in the underpinning graph give insights into the number and length distribution of attractors in the NK model. We use a fast direct circuit enumeration algorithm to study the NK model and determine the growth behaviour of structural circuits. This leads to an explanation and lower bound on the growth properties and the number of attractor loops and a possible K-relationship for circuit number growth with network size N. We also introduce a mixed-K model that allows us to explore <K> between pairs of integer K values in Kauffman-like systems. We find that the circuits' behaviour is a useful metric in identifying phase transitional behaviour around the critical connectivity in that model too. We identify an intermediate phase transition in circuit growth behaviour at K_S approximately 1.5, that is distinct from both the percolation transition at K_P = 1 and the Kauffman transition at K_C = 2. We relate this transition to mutual node reachability within the giant component of nodes.