title: Irreversibility and self-organization in hydrodynamic echo experiments.
abstract: We discuss the reversible-irreversible transition in low-Reynolds hydrodynamic systems driven by external cycling actuation. We introduce a set of models with no auto-organization, and show that a sharp crossover is obtained between a Lyapunov regime in which any noise source, such as thermal noise, is amplified exponentially, and a diffusive regime where this no longer holds. In the latter regime, groups of particles are seen to move cooperatively, yet no spatial organization occurs.
authors.affiliation: Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, CNRS UMR 8550-Université Paris 6-Université Paris 7, 24, rue Lhomond, 75005 Paris, France.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Düring
authors.forename: Denis
authors.initials: D
authors.lastname: Bartolo
authors.forename: Jorge
authors.initials: J
authors.lastname: Kurchan