Non-assortative structures in complex networks

The study of large complex networks often involves the partition of nodes into groups based on their connectivity. In the study of online social networks, this partition is used to identify users that belong to the same community or that play a similar role in the organization of the network. The majority of computational methods to obtain such partitions divides the nodes in assortative communities in which nodes link preferentially to other nodes in the same community. In this talk I will argue that (i) the a priori focus on assortative structures has led to the wrong impression that this is the only relevant structure in networks; (ii) that other non-assortative structures are ubiquitous in complex networks and important to understand their organization. These conclusions is based on a methodology we introduce to classify the relationship between groups of nodes in networks, which is applied systematically to 52 different networks and to two social-media networks (as case studies). Reference: C. X. Liu, T. J. Alexander, and E.G. Altmann: "Non-assortative relationships between groups of nodes are typical in complex networks" , PNAS Nexus, pgad364 (2023), academic.oup.com/pnasnexus/article/2/11/pgad364/7367864