Self-organization of structures and networks from merging and   small-scale fluctuations
  We discuss merging-and-creation as a self-organizing process for scale-free topologies in networks. Three power-law classes characterized by the power-law exponents 3/2, 2 and 5/2 are identified and the process is generalized to networks. In the network context the merging can be viewed as a consequence of optimization related to more efficient signaling. 
P. Minnhagen, M. Rosvall, K. Sneppen, and A. Trusina