When: Lunedì 7 Maggio 2007, ore 14.30
Where: Aula 1201, Dipartimento di Matematica, Università di Roma "Tor Vergata"
Who: Prof. Thierry Gobron, CNRS - Université de Cergy Pontoise
Title: Attractiveness and couplings for conservative particle systems. (Joint work with E. Saada, CNRS - Université de Rouen)
Abstract: Attractiveness is a fundamental tool in the study of interacting particle systems. For the basic example of simple exclusion, this property is shown to hold through the basic coupling construction, which proves the existence of a markovian coupled process $(\xi_t,zeta_t)_{t\geq 0}$ that satisfies:
(P) for any two initial configurations $\xi_0\leq\zeta_0$ (coordinate-wise), $\xi_t\leq\zeta_t$ a.s. for all $t\geq 0$.
We generalize this classical result in two ways, in which the basic coupling construction is not possible: In one part, we consider conservative particle systems on $\Z^d$ for which, in each transition, $k$ particles can jump between sites, with $1\leq k$. In the second part, we consider exclusion systems with interaction. In both cases, we give necessary and sufficient conditions on the rates underwhich those systems are attractive, and give some details on the construction of a markovian coupled process satisfying (P). We also prove that under such a coupling, the number of discrepancies between the two copies of the process is decreasing in time.