The Order-disorder Transition in Incompressible Polar Active Fluids with an Easy Axis

Leiming Chen; Chiu Fan Lee; John Toner

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arXiv · 2507.15159

The Order-disorder Transition in Incompressible Polar Active Fluids with an Easy Axis

Leiming Chen·Chiu Fan Lee·John Toner

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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.

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BibTeX RIS

Leiming Chen, Chiu Fan Lee, John Toner. 2025-07-20. The Order-disorder Transition in Incompressible Polar Active Fluids with an Easy Axis. https://arxiv.org/abs/2507.15159

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