Abstract
Abstract.: We study the flocking model introduced by Vicsek et al. (Phys. Rev. Lett. 75, 1226 (1995)) in the “coarsening” regime. At standard self-propulsion speeds, we find two distinct growth laws for the coupled density and velocity fields. The characteristic length scale of the density domains grows as Lρ(t)∼tθρ (with θρ≃ 0. 25 , while the velocity length scale grows much faster, viz., Lv(t)∼tθv (with θv≃ 0. 83 . The spatial fluctuations in the density and velocity fields are studied by calculating the two-point correlation function and the structure factor, which show deviations from the well-known Porod’s law. This is a natural consequence of scattering from irregular morphologies that dynamically arise in the system. At large values of the scaled wave vector, the scaled structure factors for the density and velocity fields decay with powers -2.6 and -1.52 , respectively. Graphical abstract: [Figure not available: see fulltext.].