Physics (Internal)

Spontaneous Recovery and Metastability in Single and Interdependent Networks

This event is part of the Departmental Seminars.

PhD Committee: H.E.Stanley, Lawrence Sulak, Rama Bansil, William Skocpol, Shlomo Havlin/Irena Vodenska.

Abstract: Many complex systems can be described as networks consisting of units (nodes) connected with links. Examples range from biology, to transportation and finance. Much research has been carried out on exploring the vulnerability of such network systems. Of particular interest are abrupt dynamic events that cause networks to irreversibly fail. However, in many real-world phenomena such as brain seizures in neuroscience or sudden market crashes in finance, after an inactive period of time a significant part of the damaged network is able to become spontaneously active again. The process often occurs repeatedly. To model this dynamic of network recovery in both single and interdependent networks, we examine the effect of local node recoveries and stochastic contiguous spreading and find that they can lead to the emergence of macroscopic phase-flipping phenomena between different levels of activity. We study phase diagrams of single and interdependent networks. The phase diagram gets exponentially complicated with the increasing number of networks in interaction. In interdependent networks, knowing and understanding the phase diagram has an immediate practical implication; it enables us to find the optimal strategy for repairing interconnected networks that are fully or partially damaged. To support the model, we study an example of a real interacting financial network, where we find evidence of fast dynamical transitions between well defined metastable states, in agreement with predictions of our model.