Fluctuations, renormalizations, and a convective instability in driven wet active matter

TL;DR

This paper investigates a scalar model of wet active matter under temperature or chemical potential gradients, revealing a convective instability driven by activity, with analysis of correlations, Casimir forces, and fluid dynamics near the instability.

Contribution

It introduces a scalar model for wet active matter with an imposed gradient, analyzing the instability, correlations, and generalized Lorenz equations in a non-equilibrium setting.

Findings

Identification of a convective instability driven by activity.

Calculation of long-ranged correlations and Casimir forces.

Derivation of generalized Lorenz equations for active fluid behavior.

Abstract

A scalar model of wet active matter in the presence of an imposed temperature gradient, or chemical potential gradient, is considered. It is shown that there is a convective instability driven by a (negative) activity parameter. In this non-equilibrium steady state the generic long-ranged correlations are computed and compared and contrasted with the analogous results in a passive fluid. In addition, the non-equilibrium Casimir pressure or force is computed. Singularities in various physical quantities as the instability is approached are determined. Finally, we give the generalized Lorenz equations characterizing the fluid behavior above the instability and contrast these equations to the Lorenz equations for the Rayleigh-Bernard instability in a passive fluid.