Scale-Free Networks are Ultrasmall

Abstract
We study the diameter, or the mean distance between sites, in a scale-free network, having N sites and degree distribution p(k) ~ k^-a, i.e. the probability of having k links outgoing from a site. In contrast to the diameter of regular random networks or small world networks which is known to be d ~ lnN, we show, using analytical arguments, that scale free networks with 22, one can construct a deterministic scale free network with d ~ lnlnN, and this construction yields the lowest possible diameter.