Department of Physics
Bar-Ilan University, Israel
Monday Oct. 18, 2010, 3:00-4:00PM, CS Conference Room
Abstract: In interdependent networks, when nodes in one network fail, they cause dependent nodes in another network to also fail. This may happen recursively and can lead to a cascade of failures. In fact, a failure of a very small fraction of nodes in one network may lead to the complete fragmentation of a system of many interdependent networks.
I will present a framework for understanding the robustness of interacting networks subject to such cascading failures and provide a basic analytic approach that may be useful in future work. I will present exact analytical solutions for the critical fraction of nodes that upon removal will lead to a failure cascade and to a complete fragmentation of two interdependent networks in a first order percolation transition . Surprisingly, analyzing complex systems as a set of interdependent networks may alter a basic assumption that network theory has relied on: while for a single network a broader degree distribution of the network nodes results in the network being more robust to random failures, for interdependent networks, the broader the distribution is, the more vulnerable the networks become to random failure.
We also show  that reducing the coupling between the networks leads to a change from a first order percolation phase transition to a second order percolation transition at a critical point. These findings pose a significant challenge to the future design of robust networks that need to consider the unique properties of interdependent networks.
 S. Buldyrev, R. Parshani, G. Paul, H.E. Stanley, S. Havlin, Nature, 465, 0893 (2010)
 R. Parshani, S. Buldyrev, S. Havlin, PRL, 105, 048701 (2010)
Speaker Biography: Shlomo Havlin is a Professor in the Department of Physics at Bar-Ilan University, Israel. He is an Editor in several physics journals, has published over 600 articles in international journals, co-authored and co-edited 11 books. He won numerous awards for his work including the Weizmann Prize (2009) in Israel and the APS Lilienfeld Prize (2010) in USA.
More information about him is available at: http://havlin.biu.ac.il/