Clustering properties of a generalized critical Euclidean network.

Many real-world networks exhibit a scale-free feature, have a small diameter, and a high clustering tendency. We study the properties of a growing network, which has all these features, in which an incoming node is connected to its ith predecessor of degree k(i) with a link of length l using a probability proportional to k(beta)(i)l(alpha). For alpha>-0.5, the network is scale-free at beta=1 with the degree distribution P(k) proportional to k(-gamma) and gamma=3.0 as in the Barabási-Albert model (alpha=0,beta=1). We find a phase boundary in the alpha-beta plane along which the network is scale-free. Interestingly, we find a scale-free behavior even for beta>1 for alpha<-0.5, where the existence of a different universality class is indicated from the behavior of the degree distribution and the clustering coefficients. The network has a small diameter in the entire scale-free region. The clustering coefficients emulate the behavior of most real networks for increasing negative values of alpha on the phase boundary.