Résumé
The surprising collective phenomena that emerge when particles can move autonomously have inspired many physicists to join the field of active matter. In sharp contrast to the delta-correlated thermal motion of (dead) particles in equilibrium, the autonomous motion of active particles is correlated over finite time scales. Recently, the emergence of complex chaotic flows that phenomenologically resemble turbulence and appear in a range of biological and physical active matter systems has attracted much interest. In this talk, I will show that even the simplest model of active particles -- self-propelled point particles -- can feature mesoscale flows with streams and vortices, i.e. a form of 'active turbulence'. Emergence of these collective flows is surprising as there are strictly no spatial correlations in the forces particles use to self-propel. I will furthermore show that another simple model where self-propulsion forces are spatially correlated displays similar chaotic flows, suggesting the possibility of a universality class distinct from the current classification scheme by Alert et al. 2022.