Dry active turbulence in microtubule-motor mixtures

TL;DR

This paper investigates the complex dynamics of microtubule-motor mixtures, revealing how simple physical mechanisms lead to diverse patterns like stable stripes and chaotic behaviors, unifying previous observations in dry active matter.

Contribution

It introduces a minimal continuum model derived from microscopic interactions that explains pattern formation and chaos in microtubule-motor systems.

Findings

Stable stripe patterns emerge from motor-induced interactions.

Chaotic, never-settling patterns are observed in simulations.

The minimal model captures the essential physics of the full system.

Abstract

We study the dynamics and phase behaviour of a dry suspension of microtubules and molecular motors. We obtain a set of continuum equations by rigorously coarse graining a microscopic model where motor-induced interactions lead to parallel or antiparallel ordering. Through numerical simulations, we show that this model generically creates either stable stripes, or a never-settling pattern where stripes periodically form, rotate and then split up. We derive a minimal model which displays the same instability as the full model, and clarifies the underlying physical mechanism. The necessary ingredients are an extensile flux arising from microtubule sliding and an interfacial torque favouring ordering along density gradients. We argue that our minimal model unifies various previous observations of chaotic behaviour in dry active matter into a general universality class.