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Gossip: Identifying Central Individuals in a Social Network

How can we identify the most influential nodes in a network for initiating diffusion? Are people able to easily identify those people in their communities who are best at spreading information, and if so, how? Using theory and recent data, we examine these questions and see how the structure of social networks affects information transmission ranging from gossip to the diffusion of new products. In particular, a model of diffusion is used to define centrality and shown to nest other…

On a High-Dimensional Random Graph Process

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We introduce a model for a high-dimensional random graph process and ask how "rich" the process has to be so that one finds atypical behavior. In particular, we study a natural process of Erdös-Rényi random graphs indexed by unit vectors in R^d . We investigate the deviations of the process with respect to three fundamental properties: clique number, chromatic number, and connectivity. The talk is based on joint work with Louigi Addario-Berry, Shankar Bhamidi, Sebastien Bubeck, Luc Devroye, and Roberto…

MOCCA: a primal/dual algorithm for nonconvex composite functions with applications to CT imaging

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Many optimization problems arising in high-dimensional statistics decompose naturally into a sum of several terms, where the individual terms are relatively simple but the composite objective function can only be optimized with iterative algorithms. Specifically, we are interested in optimization problems of the form F(Kx) + G(x), where K is a fixed linear transformation, while F and G are functions that may be nonconvex and/or nondifferentiable. In particular, if either of the terms are nonconvex, existing alternating minimization techniques may…


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