The significant advances realized in recent years in the study of complex networks are severely limited by an almost exclusive focus on the behavior of single networks. However, most networks in the real world are not isolated but are coupled and hence depend upon other networks, which in turn depend upon other networks. Real networks communicate with each other and may exchange information, or, more importantly, may rely upon one another for their proper functioning. A simple but real example is a power station network that depends on a computer network, and the computer network depends on the power network. Our social networks depend on technical networks, which, in turn, are supported by organizational networks. Surprisingly, analyzing complex systems as coupled interdependent networks alters the most basic assumptions that network theory has relied on for single networks. A multidisciplinary, data driven research project will: 1) Study the microscopic processes that rule the dynamics of interdependent networks, with a particular focus on the social component; 2) Define new mathematical models/foundational theories for the analysis of the robustness/resilience and contagion/diffusive dynamics of interdependent networks. This project will afford the opportunity of greatly expanding the understanding of realistic complex networks by joining theoretical analysis of coupled networks with extensive analysis of appropriately chosen large-scale databases. These databases will be made publicly available, except for special cases where it is illegal to do so.
This research has important implications for the understanding the social and technical systems that make up a modern society. A recent US Scientific Congressional Report concludes ?No currently available modeling and simulation tools exist that can adequately address the consequences of disruptions and failures occurring simultaneously in different critical infrastructures that are dynamically inter-dependent.? Understanding the interdependence of networks and its effect on the system robustness and on the structural and functional behavior is crucial for properly modeling many real world systems and applications, from disaster preparedness, to building effective organizations, to comprehending the complexity of the macro economy. In addition to these intellectual objectives, the research project includes the development of an extensive outreach program to the public, especially K-12 students.