Before revision:  By mapping the evolutionary process into a statistical ensemble , and minimizing its associated free energy, we find the structural properties which emerge as the selective pressure is increased , and identify a phase transition from a random topology to a "segregated core" structure, where a smaller and more densely connected subset of the nodes is responsible for most of the regulation in the network.
After revision:  By mapping the evolutionary process into a statistical ensemble and minimizing its associated free energy, we find the structural properties which emerge as the selective pressure is increased , and identify a phase transition from a random topology to a "segregated core" structure, where a smaller and more densely connected subset of the nodes is responsible for most of the regulation in the network.