  In this paper we present a new version of a network growth model, generalized
in order to describe the behavior of social networks. The case of study
considered is the preprint archive at cul.arxiv.org. Each node corresponds to a
scientist, and a link is present whenever two authors wrote a paper together.
This graph is a nice example of degree-assortative network, that is to say a
network where sites with similar degree are connected each other. The model
presented is one of the few able to reproduce such behavior, giving some
insight on the microscopic dynamics at the basis of the graph structure.
