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Martedi' 22 ottobre 2013, alle 14.30, nell'Aula B del Dip. di Matematica dell'Universita' La Sapienza, si terra' si seguente seminario
Speaker: Pietro Caputo (Universita' di Roma III) Title: Large deviations in sparse random graphs: a local weak convergence approach
Abstract: Consider the Erdos-Renyi random graph on n vertices where each edge is present independently with probability p = c/n, with c > 0 fixed. For large n, a typical realization locally behaves like the Galton-Watson tree with Poisson offspring distribution with mean c. We discuss large deviations from this typical behavior, within the framework of the local weak convergence introduced by Benjamini-Schramm and Aldous-Steele. The associated rate function is expressed in terms of an entropy functional on unimodular measures and takes finite values only at measures supported by trees. Along the way, we present a new configuration model which allows one to sample uniform random graphs with a given finite neighborhood distribution, provided the latter is supported by trees. We also present a new class of unimodular random trees, which generalizes the Galton-Watson tree with given degree distribution to the case of neighborhoods of arbitrary finite depth. This is joint work with Charles Bordenave.