Active Matter -The Physics of Self-Organization

Birds flock, bees swarm and fish school. These are just some of the remarkable examples of collective behavior found in nature. Physicists have been able to capture some of this behavior by modeling organisms as "flying spins" that align with their neighbors according to simple but noisy rules. Successes like these have spawned a field devoted to the physics of active matter - matter made not of atom and molecules but of entities that consume energy to generate their own motion and forces. Through interactions, collectives of such active particles organize in emergent structures on scales much larger than that of the individuals. The paradigm of such behavior are living systems, but same behavior has also been mimicked in the lab through the engineering a variety of “active particles’’ that self-assemble to form smart materials.

In this lecture I will introduce the field of active matter and highlight ongoing efforts by physicists, biologists, engineers and mathematicians to model the complex behavior of these systems, with the goal of identifying universal principles. I will specifically focus on two examples of active behavior. The first highlights how active particles bypass the laws of equilibrium thermodynamics and spontaneously aggregate in the absence of any attractive interactions. The second describes the interplay of flow and topological defects in controlling dynamics and structure of active phases with liquid crystalline order, with relevance on scales from subcellular to entire organisms.

Speaker: Cristina Marchetti, UC Santa Barbara