The Statistical Mechanics of Active Interfaces, Bubbles, and Membranes

Thermodynamics is among the most successful frameworks in the physical sciences because it explains how and why systems at or near equilibrium undergo dramatic transformations. Yet many living and active systems are sustained far from equilibrium, where the usual thermodynamic framework need not apply. In this talk, I will provide a broad overview of my group’s efforts to develop a statistical-mechanical description of interfacial phenomena in such systems. Starting from microscopic dynamics and systematically coarse-graining to continuum fields, we recover analogues of familiar concepts such as surface tension and nucleation barriers, while revealing how activity and nonconservative forces modify them. I will show how this mechanical framework can describe the formation, fluctuations, and stability of active interfaces, bubbles, and membranes, comparing its predictions with simulations and experiments. Together, these results help clarify which equilibrium concepts remain useful far from equilibrium and how they must be generalized when they do.

Speaker: Ahmad Omar, UC Berkeley