Evolution of the social network of scientific collaborations

Evolution of the social network of scientific collaborations1,2 1 1,2,∗ 1 3 2,4A.L. Baraba´si , H. Jeong , Z. N´eda , E. Ravasz , A. Schubert , T. Vicsek1Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA2 Collegium Budapest, Institute of Advanced Study, Budapest, Hungary3 Bibliometric Service, Library of the Hungarian Academy of Sciences, Budapest, Hungary4Department of Biological Physics, E¨otv¨os Lor´and University, Budapest, Hungary(Last revised February 1, 2008)The co-authorship network of scientists represents a prototype of complex evolving networks. Inaddition, it offers one of the most extensive database to date on social networks. By mapping theelectronic database containing all relevant journals in mathematics and neuro-science for an eight-yearperiod(1991-98), weinferthedynamicandthestructuralmechanismsthatgoverntheevolutionandtopology ofthiscomplexsystem. Threecomplementaryapproachesallowustoobtainadetailedcharacterization. First, empirical measurements allow us to uncover the topological measures thatcharacterize the network at a given moment, as well as the time evolution of these quantities.The results indicate that the network is scale-free, and that the network evolution is governed bypreferential attachment, affecting both internal and external links. However, in contrast with mostmodel predictions the average degree increases in time, and the node separation decreases. Second,we propose a simple model that ...