Where does everybody go? Active particles under position-dependent interactions

F. PERUANI; L. BARBERIS

Workshop; Latin American School and Workshop on Data Analysis and Mathematical Modeling of Social Science; 2016

CELFI

Navigation in animals and humans strongly depends on their interaction with their environment.For animals capable of vision, and depending on the conformation of their sensory organs (eyes), side viewing angle and cognitive horizon limit the interaction to a ?cone of vision? (CV).I present a system of active particles interacting through an attractive short-range social force, which solely depends on the position and is restricted to a CV. Since CV breaks Newton?s third law, this systemcan display various patterns of complex self-organization at a macroscopic scale that correspond to social patterns observed in nature.Depending on the values of the parameters we can observe: (a) The formation of polar lines whose heading particles act as effective leaders, similarly to what is observed in sheep. (b) Phase separation into droplets with different structures, some of them similar to schools of fish and other swarms. (c) Nematic structure formation with long range order, similar to pedestrian traffic lines or ant columns.Combining computer simulations and nonlinear field equations I show that position-based active particle models belong to a new class of active systems. In particular, they are very different from other well-known systems such as those that consider velocity alignment (Vicsek models).These results are of importance for the study, interpretation, modeling and/or design of collective patterns of active particle systems both live and synthetic.