Kinetic Theory of Active Particles : Correlation and Memory Effects
Lundi 30 octobre 2017 14:00
- Duree : 1 heure
Lieu : Conference room - LIPhy - Bât E - 140 Avenue de la Physique - St Martin d’Hères. Accès par interphone, appeler le secrétariat
Orateur : Thomas IHLE (Greifswald University, Germany)
We consider Vicsek-type models for self-propelled agents. In these models, active agents try to align their travel directions with the average direction of their neighbors plus some noise. At low noise, a globally ordered state of collective motion forms. Starting from the exact evolution equation for the N-particle probability distribution, using the Molecular Chaos assumption an Enskog-like kinetic equation is derived, which is solved numerically. Steep soliton-like waves are observed that lead to an abrupt jump of the global order parameter if the noise level is changed. The shape of the waves is shown to quantitatively agree with agent-based simulations at large speeds. Often, Molecular Chaos is invalid near the onset of collective motion, and correlation effects become relevant. It is shown how to self-consistently include correlations at the level of ring-kinetic theory. For a particular Vicsek-style model with bounded confidence interactions, we observe the so-called Kovacs-effect. This effect becomes huge under certain conditions and describes strong memory effects. This provides an indirect proof that the usual Toner-Tu theory for polar active matter should not be applicable here. A nonlinear theory for the Kovacs effect is developed, which agrees quantitatively with our data.
Contact : chaouqi.misbah@univ-grenoble-alpes.fr
Discipline évènement : (Physique)
Entité organisatrice : (LIPhy)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire Mat. Molle/grise)
Site de l'évènement : Domaine Universitaire de St Martin d’Hères
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