Thermodynamically consistent flocking: From discontinuous to continuous transitions

• DOI: 10.48550/arxiv.2401.09901
• Publication Date: 2024-01-01
• Authors: Tal Agranov; Robert L. Jack; M. E. Cates; Étienne Fodor
• Keywords: Flocking (texture); Tricritical point; Binodal; Lattice (music)

We introduce a family of lattice-gas models flocking, whose thermodynamically consistent dynamics admits proper equilibrium limit at vanishing self-propulsion. These are amenable to an exact coarse-graining which allows us study their hydrodynamic behavior analytically. show that the here belongs universality class Model C, and it generically exhibits tricritical behavior. Self-propulsion has non-perturbative effect on phase diagram, yielding novel behaviors depending type aligning interactions. For interactions increase monotonically with density, point diverges infinite density reproducing standard scenario discontinuous flocking transition accompanied by traveling bands. In contrast, for where interaction is non-monotonic in system can exhibit either (the nonequilibrium counterpart of) azeotropic point, associated continuous transition, or state counterpropagating