Figure 8

Authors flow across fields against null model. For each time window (2 years), PACS are disposed in a circle. The width of each arc is proportional to the number of authors who published at least one paper in that field (and that published at least another one the year after). Each field is represented by its PACS number, see Table 1. Links represent the number of authors who, having published at least one paper in the source field on the right, also publish at least one paper in the target field on the left (at seen from outside the circle). Only significative links are considered—i.e. links with a Z-score equal or larger than 2 with respect to a null model where links are reshuffled preserving nodes degree and strength. Note that an author can publish papers in several fields in a given time window so that a link does not mean that she changed her field but that, at least, she has some interest on it