Smart, Living & Active Matter - Leiden

Leiden Institute of Physics

About us

The SLAM - Smart, Living, & Active Matter - initiative unites theory and experimental groups of the Leiden Institute of Physics. It currently gathers the groups of Luca Giomi, Louise Jawerth, Daniela Kraft, Martin van Hecke, Silke Henkes and Alexandre Morin.

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2023-12-07 - 13:30 @

SLAM SEMINAR: Yann-Edwin Keta

Title: Emergence of disordered collective motion in dense systems of isotropic self-propelled particles

Abstract: Active matter is a broad class of materials within which individual entities consume energy in order to perform movement. These are thus out of thermodynamic equilibrium and display a wealth of surprising phenomena which challenge our conception of equilibrium phases and dynamics. We pay specific attention to collective motion, which has been shown to emerge in systems as diverse as crowds, flocks, schools, or swarms, yet with common characteristics. We focus in particular on one of the simplest class of active matter models, namely athermal particles with isotropic self-propulsions in 2D, which is a good approximation for dense cell tissues or self-propelled colloids. We find in size-polydisperse systems that an homogeneous active liquid exists at arbitrary large persistence times, and is characterized by remarkable velocity correlations and irregular turbulent-like flows. At large density, it undergoes a nonequilibrium glass transition. This is accompanied by collective motion, whose nature evolves from near-equilibrium spatially heterogeneous dynamics at small persistence, to a qualitatively different intermittent dynamics when persistence is large. We show that these different collective phenomena are ruled by the competition between three fundamental time scales: the intrinsic persistence and interaction time scales, and the emerging relaxation time scale. (1) (2) (3)