Tracking Modularity in Citation Networks

Clustering using cocitation and bibliographic coupling is an effective tool to analyze the structure of scientific research, but its arbitrariness in the setting of a clustering threshold is a problem. This study tracked modularity of citation networks in research domains, and we found that there are three stages in clustering of citation networks and it is universal across our case studies. In the first stage, core clusters in the domain are formed. In the second stage, peripheral clusters are formed, while core clusters continue to grow. In the third stage, core clusters grow again. By focusing on the elementary process in clustering, we can understand the structure of citation networks in each research domain and judge the location of each cluster and paper, which cannot be seen in the final clustering results