On the spontaneous collective motion of active matter

TL;DR

This paper investigates how active matter, like the cytoskeleton, exhibits spontaneous collective motion driven by energy-consuming motors, revealing conditions under which organized flow and structures emerge.

Contribution

It combines numerical and analytical methods to analyze how motor step size and response lead to collective motion and structure formation in active matter models.

Findings

Flow and oscillations emerge at higher motor step sizes.

Negative susceptibility motors create negative-temperature systems.

Structured formations resemble cell division asters.

Abstract

Spontaneous directed motion, a hallmark of cell biology, is unusual in classical statistical physics. Here we study, using both numerical and analytical methods, organized motion in models of the cytoskeleton in which constituents are driven by energy-consuming motors. While systems driven by small-step motors are described by an effective temperature and are thus quiescent, at higher order in step size, both homogeneous and inhomogeneous, flowing and oscillating behavior emerges. Motors that respond with a negative susceptibility to imposed forces lead to an apparent negative-temperature system in which beautiful structures form resembling the asters seen in cell division.