Active nematics are intrinsically phase-separated

TL;DR

This paper demonstrates through numerical simulations that active nematic systems are inherently phase-separated at steady state, exhibiting giant fluctuations similar to those predicted in earlier theories, with implications for experiments in granular and biological systems.

Contribution

It reveals that active nematics are intrinsically phase-separated, challenging previous notions of their fluctuation behavior and providing new insights into their steady-state properties.

Findings

Active nematics are macroscopically phase-separated.

Steady states exhibit giant number fluctuations.

Numerical results align with the Das-Barma model predictions.

Abstract

Two-dimensional nonequilibrium nematic steady states, as found in agitated granular-rod monolayers or films of orientable amoeboid cells, were predicted [Europhys. Lett. {\bf 62} (2003) 196] to have giant number fluctuations, with standard deviation proportional to the mean. We show numerically that the steady state of such systems is {\em macroscopically phase-separated}, yet dominated by fluctuations, as in the Das-Barma model [PRL {\bf 85} (2000) 1602]. We suggest experimental tests of our findings in granular and living-cell systems.