title: Effect of social group dynamics on contagion.
abstract: Despite the many works on contagion phenomena in both well-mixed systems and heterogeneous networks, there is still a lack of understanding of the intermediate regime where social group structures evolve on a similar time scale to individual-level transmission. We address this question by considering the process of transmission through a model population comprising social groups which follow simple dynamical rules for growth and breakup. Despite the simplicity of our model, the profiles produced bear a striking resemblance to a wide variety of real-world examples--in particular, empirical data that we have obtained for social (i.e., YouTube), financial (i.e., currency markets), and biological (i.e., colds in schools) systems. The observation of multiple resurgent peaks and abnormal decay times is qualitatively reproduced within the model simply by varying the time scales for group coalescence and fragmentation. We provide an approximate analytic treatment of the system and highlight a novel transition which arises as a result of the social group dynamics.
authors.affiliation: Physics Department, University of Miami, Coral Gables, Florida 33126, USA.
authors.forename: Zhenyuan
authors.initials: Z
authors.lastname: Zhao
authors.forename: J P
authors.initials: JP
authors.lastname: Calderón
authors.forename: Chen
authors.initials: C
authors.lastname: Xu
authors.forename: Guannan
authors.initials: G
authors.lastname: Zhao
authors.forename: Dan
authors.initials: D
authors.lastname: Fenn
authors.forename: Didier
authors.initials: D
authors.lastname: Sornette
authors.forename: Riley
authors.initials: R
authors.lastname: Crane
authors.forename: Pak Ming
authors.initials: PM
authors.lastname: Hui
authors.forename: Neil F
authors.initials: NF
authors.lastname: Johnson