Order-disorder transition in incompressible polar active fluids with an easy axis
Phys. Rev. E 113, 054142 – Published 29 May, 2026
DOI: https://doi.org/10.1103/5zhk-xtk2
Abstract
Dry active matter in an anisotropic medium is of experimental relevance, and the interplay between anisotropy and the dynamics of the active matter remains under-explored. Here, we derive the hydrodynamic equations of a generic dry polar active fluid that preferentially flows along a particular axis induced by the anisotropy of the medium. We then study its critical behavior at the order-disorder transition in which the symmetry between “forward” and “back” along the special axis is spontaneously broken. We obtain the critical static and dynamic exponents, mean velocity, and two-point correlation functions exactly in three dimensions, and to two-loop level in two dimensions, by mapping our class of systems to the equilibrium Ising model with dipolar interactions.
