Mesure de l'intensité de collaboration dans la recherche scientifique et évaluation du rôle de la distance géographique

In order to study networks of collaboration between researchers, we propose a simple measure of the intensity of collaboration, which can be easily interpreted in terms of relative probability and directly aggregated at the laboratory level. We use it to characterize the relations of collaboration, as defined in terms of co-publication, between the physicists the French Centre National de la Recherche Scientifique (CNRS), in the field of condensed-matter, between 1992 and 1997, and to analyse if their intensity of collaboration depends on the geographical distance between laboratories. We find that the average intensity of co-publication within laboratories is about 40 times higher than the intensity between laboratories but within towns, and 100 times higher than the intensity between laboratories and between towns. Yet, geographical distance does not have a significant impact, or a very weak one, on the existence and intensity of co-publication of researchers located in different towns.