Swimmer suspensions on substrates: anomalous stability and long-range order
Abstract
We present a comprehensive theory of the dynamics and fluctuations of a two-dimensional suspension of polar active particles in an incompressible fluid confined to a substrate. We show that, depending on the sign of a single parameter, a state with polar orientational order is anomalously stable (or anomalously unstable), with a nonzero relaxation (or growth) rate for angular fluctuations at zero wavenumber. This screening of the broken-symmetry mode in the stable state does lead to conventional rather than giant number fluctuations as argued by Bricard et al., Nature , 95 (2013), but their bend instability in a splay-stable flock does not exist and the polar phase has long-range order in two dimensions. Our theory also describes confined three-dimensional thin-film suspensions of active polar particles as well as dense compressible active polar rods, and predicts a flocking transition without a banding instability
Cite
@article{arxiv.1901.01069,
title = {Swimmer suspensions on substrates: anomalous stability and long-range order},
author = {Ananyo Maitra and Pragya Srivastava and M. Cristina Marchetti and Sriram Ramaswamy and Martin Lenz},
journal= {arXiv preprint arXiv:1901.01069},
year = {2020}
}