Micro-dynamics in the PACS network.
Examples of (a) the appearance of new links that increase the density of a local neighborhood: a large number of links appear between some sub-fields of condensed matter and general physics, (b) the appearance of new nodes (03.75, 74.25) and links increasing the density and (c) changes in the network structure, where a new node (61.05) replaces several existing nodes (61.10, 61.12, 61.14). Probability of link appearance as a function of the (d) distance d and (e) number of common neighbors nCN between the nodes. Probability of appearance of new nodes as a function of the (f) d and (g) nCN between the nodes. The links categorized according to the hierarchical similarity h of the nodes they are connecting. (h) Similarity of discontinued nodes (circles) and newly introduced nodes (squares) with their maximally similar counterpart nodes, as measured by the overlap . The overlap is averaged over focal node strength. (i) The fraction of maximally similar nodes that appear around the disappearance of the focal node (circles) (from one year before the disappearance to one year after) and the fraction of maximally similar nodes that have disappeared around the time of appearance of the focal node (squares), again as a function of focal node strength.