Sommaire:

Self-propelled particles convert energy from their surrounding environment into translational motion. Collectively, they are generically able to inject local energy into the macroscopic motion of the whole system, thus sustaining an orientationally ordered stationnary state in two dimensions. In this talk, I will discuss the transition between this polar state (whose existence is forbidden for equilibrium systems) and the less exotic isotropic state. A key observation is that the interaction of self-propelled particles does not conserve momentum. I will show how this can be made more quantitative in the dilute regime, in order to obtain predictions on the transition between isotropic and polar phases. Although the theory is general, I will focus the discussion on a model of self-propelled hard discs that was already shown to describe very well a vibrated grain experiment. The quantitative predictions of the theory are checked against data from molecular dynamics simulations. I will finally discuss our recent findings about how density effects alter the mean-field transition.

Pour plus d'informations, merci de contacter Berthier L.