Collective Phenomena in Active Systems

Erwin Frey, LMU Munich

Active systems are many-body systems where the constituent particles are either self-propelled or externally driven. Examples include flocks of animals and cohorts of cells in tissue, intracellular transport and cytoskeletal networks, and fluctuating granular matter. These systems exhibit a rich spectrum of steady states and emergent phenomena. Traffic jams of molecular motors along microtubules regulate the length of these cytoskeletal filaments. Assemblies of biopolymers and molecular motors self-organize into coherent swarms and density waves and thereby drive cytoskeletal organization. Vibrated granular matter may either form strongly fluctuating states with short-lived structures that are continually created and destroyed, or long-lived patterns and jammed states. In this talk we give an overview of these active systems and review recent progress in applying principles of non-equilibrium statistical mechanics and kinetic theory to understand some of the mechanisms underlying the observed collective phenomena.