Special CPM Seminar

Universality in Soft Active Matter

Chiu Fan Lee

Department of Bioengineering
Imperial College London

Biology systems operate in the far from equilibrium regime and one defining feature of living organisms is their motility. In the hydrodynamic limit, a system of motile organisms may be viewed as a form of active matter, which has been shown to exhibit behaviour analogous to that found in equilibrium systems, such as phase separation in the case of motility-induced aggregation, and critical phase transition in incompressible active fluids. In this talk, I will use the concept of universality to categorise some of the emergent behaviour observed in active matter. Specifically, I will show that i) the coarsening kinetics of motility-induced phase separation belongs to the Lifshitz-Slyozov-Wagner universality class [1]; ii) the order-disorder phase transition in incompressible polar active fluids (IPAF) constitutes a novel universality class [2], and iii) the behaviour of IPAF in the ordered phase in 2D belongs to the Kardar-Parisi-Zhang universality class [3].

References:
[1] C. F. Lee, “Interface stability, interface fluctuations, and the Gibbs-Thomson relation in motility-induced phase separations,” arXiv:1503.08674, 2015.
[2] L. Chen, J. Toner, and C. F. Lee, “Critical phenomenon of the order-disorder transition in incompressible active fluids,” New Journal of Phyics, 17, 042002, 2015.
[3] L. Chen, C. F. Lee, and J. Toner, “Birds, magnets, soap, and sandblasting: surprising connections to incompressible polar active fluids in 2D,” arXiv:1601.01924, 2016.