Local and global behavior of the subcritical contact process
Leonardo T. Rolla (University of Buenos Aires and NYU-Shanghai)

In this talk we will describe three fundamental objects assuming only elementary mathematical knowledge: 1) Contact process - a stochastic process that serves as a generic model for the propagation of a certain infection or rumor among a certain population (one of the simplest systems that exhibit a phase transition); 2) Marked Poisson point process - a random process consisting of set of points on the space where each point carries extra information, for instance a color or perhaps something richer such as another random process; and 3) Quasi-stationary distribution - for a stochastic evolution that is doomed to become extinct, a QSD is a probability distribution which, although does not give a steady state for the process, is a steady state when conditioning on non-extinction. We will then describe the scaling limit of the subcritical contact process in terms of a marked Poisson point process and a quasi-stationary distribution, and discuss the question of uniqueness of the QSD in this and other contexts. Based on joint works with E. Andjel, F. Ezanno and P. Groisman, with Aurelia Deshayes, and with F. Arrejoría and P. Groisman.