Abstract

Active matter comprises a wide variety of systems characterized by the continuous consumption of energy of its elementary constituents, typically converted into directed motion. As a result, active matter evolves out-of-equilibrium, lifting most of the constraints imposed by equilibrium statistical mechanics. One of the common features of these systems, is their (sometimes spectacular) collective self-organization in space and time, eventually leading to non-equilibrium phase transitions. This naturally arises the question: can we classify the large scale behavior of active systems within a limited number of ‘universality classes’, represented by some minimal models? Here I will present an overview of the collective behavior of simple models of chiral and non-chiral active particles with excluded volume interactions, in the presence (or absence) of velocity-aligning torques of different nature. I will discuss what I believe are some general features of these systems by comparing results obtained from particle-based simulations, continuum theories and recent experiments of spinning colloidal suspensions.