Date: January 4, 2007
Department: Charlton College of Business
The findings by Braha and Yaneer Bar-Yam, president of the New England Complex Systems Institute (NECSI), are based on a study of the behavior of 57,000 email users over a period of four months. "There should be a radical change in how we think about networks and the individuals who are part of them," Braha said. "The results presented in our paper challenge the static viewpoint of complex network analysis. We now need to view networks as a collection of flickering strings rather than a collection of fixed rods."
The study of complex networks is a rapidly growing and inter-disciplinary field that seeks to understand and explain social and physical relationships of all kinds - brain structures, chemical interactions, the internet, highway systems, etc. -- and how these networks affect society.
All complex networks are built from nodes and the links between them. The nodes with the most links than others are the hubs of the network. The traditional model of complex networks has assumed that the locations of these hubs stay constant, and that the links between nodes and hubs are static.
Anti-virus software designers, for instance, rely on this model when they target the network servers that communicate the most with other computers. Similarly, one of the key strategies of Malaria vaccination efforts has been to quarantine disease-heavy villages. Braha, however, is challenging that view and arguing for a more nimble approach to confronting harmful networks.
Braha believes the development of Al-Qaeda and the 9/11 attacks serve as a dramatic illustration of his and Bar-Yam's new theory. Critics of the CIA's handling of intelligence prior to 9/11 have argued that Mohamed Atta was a network hub whose heavy volume of in- and out- going messages should have been intercepted. Braha, however, said, terrorist monitoring efforts need to be more flexible and open to changing targets, ready to identify and track people as they evolve into powerful hubs.
Braha and Bar Yam's theory also suggests that people who display chaotic and irregular social activity are the ones most likely to play the more important roles in social networks: the spread of fashion, rumors, norms, and opinions.
"The most influential people are not the ones with the biggest address books," Bar-Yam said. "What really matters is who is talking to whom. By looking only at who knows whom you lose a lot of important details about when people actually talk to each other."
Braha and Bar-Yam's paper, "From Centrality to Temporary Fame: Dynamic Centrality in Complex Networks," was a feature article in the November issue of the journal Complexity, whose editorial board includes four Nobel laureates.
Braha received his PhD in Operations Research and Industrial Engineering from Tel Aviv University, and went on to become a Professor of Engineering at Ben-Gurion University. He later traveled to America as a Visiting Professor at the Massachusetts Institute of Technology (MIT), and then worked as a Research Scientist at Boston University. He came to UMass Dartmouth in 2004, and he is currently a professor in the Department of Decision and Information Sciences at the Charlton College of Business. He is also an affiliate of NECSI. He has acted as Associate Editor for IEEE Transactions, and he is on the editorial boards of other prominent journals.
Throughout his career, he has published widely in journals such as Management Science, Physical Review, the International Journal of Production Research, and Research in Engineering Design. Braha's books include A Mathematical Theory of Design: Foundations, Algorithms, and Applications (Kluwer, 1998) which he co-authored with Oded Maimon; and most recently, Complex Engineered Systems: Science Meets Technology (Springer 2006), which he co-edited with Bar-Yam and Ali A. Minai.