Abstract

Active matter is receiving intense attention from physicists because of its importance to non-equilibrium physics and biological physics. But how different is active matter from equilibrium and non-equilibrium matter that we are familiar with? If one focuses on the large distance behaviour of a dynamical system, a powerful, stringent and unambiguous way to quantity novelty is to use renormalisation group analysis to determine whether the system’s behaviour constitutes a novel universality class (UC). This is the approach I will take in this talk. Specifically, I will start by discussing the symmetries underlying the Ising model and how the corresponding universal behaviour emerges. I will then generalise the Ising model to the active regime and discuss the emergence of other UCs. After that I will discuss the symmetries underlying the incompressible Navier-Stokes equation, generalise it to the active regime and elucidate the various UCs associated to incompressible active fluids. Overall, we will encounter eight distinct UCs in this talk, two of which are novel UCs discovered in active matter.