Diffusive regimes in a two-dimensional chiral fluid

TL;DR

This paper investigates the diffusive behavior of a two-dimensional chiral fluid composed of rotors, revealing complex diffusion regimes, odd diffusion phenomena, and a self-regulating diffusion tensor influenced by flow vorticity.

Contribution

It provides the first detailed analysis of diffusive regimes in 2D chiral fluids, highlighting the presence of odd diffusion and vorticity-dependent self-regulation.

Findings

Identification of odd diffusion with antisymmetric tensor components

Transitions between super, quasi-normal, and sub diffusion regimes

Diffusion tensor elements change sign with flow vorticity

Abstract

Diffusion is a fundamental aspect of transport processes in biological systems, and thus, in the development of life itself. And yet, the diffusive dynamics of active fluids with directed rotation, known as chiral fluids, has not been analyzed in detail so far. Here, we describe the diffusive regimes of a two-dimensional chiral fluid, composed in this case of a set of identical disk-shaped rotors. We found strong experimental evidence of odd diffusion. This odd diffusion emerges in the form of a two-dimensional tensor with an antisymmetric part. In particular, we show that chiral diffusion is complex, featuring transitions between super, quasi-normal, and sub diffusion, and very slowly aging. Moreover, we show that the diffusion tensor elements, including off-diagonal elements; i.e., odd diffusion coefficient, change sign according to flow vorticity. Therefore, the chiral fluid has a self regulated diffusion, controlled by its vorticity.