Abstract: We aggregate information, make decisions, and form opinions through interactions on social networks. In this talk, I will share some of my work on how community structures affect social contagions and opinion formations on social networks.
We study a complex contagion model on graphs with community structures. We prove that assigning all initially infected agents to a single community is the optimal seeding strategy to maximize the span of contagion. In opinion formation, we consider how community structures affect time to reach a consensus and show a sharp threshold property depending on community structures.