Abstract

We consider fluids composed of mesoscopic particles such as colloids or bacteria, driven away from equilibrium either by external fields or by self-propulsion of individual particles. Such systems support rich collective phenomena including phase separation, lane formation, and flocking. A natural expectation is that such states can be characterised by suitably extending ideas from equilibrium statistical mechanics, and theories of equilibrium phases. I will describe ongoing efforts in this direction, illustrated with examples [1,2,3]. I will explain the how the rate of entropy production [4] can be used to quantify the distance from equilibrium in these systems.

[1] F Turci, RL Jack, and NB Wilding, arXiv:2310.07531. [2] T Agranov, RL Jack, ME Cates and E Fodor, arXiv:2401.09901. [3] H Yu and RL Jack, arXiv:2305.05990. [4] E Fodor, RL Jack, and ME Cates, Ann. Rev. Cond. Matt. Phys. 13, 215 (2022)