Superdiffusion and antidiffusion in an aligned active suspension

Abstract

We show theoretically that an imposed uniaxial anisotropy leads to new universality classes for the dynamics of active particles suspended in a viscous fluid. In the homogeneous state, their concentration relaxes superdiffusively, stirred by the long-ranged flows generated by its own fluctuations, as confirmed by our numerical simulations. Increasing activity leads to an anisotropic diffusive instability, and thus an original phase-separation mechanism, driven by the interplay of active stresses with a particle current proportional to the local curvature of the suspension velocity profile.

Physics of the origin of certain terms clarified, numerical estimates improved, key references added

References in corpus (20)

• The Mechanics and Statistics of Active Matter
• Living Liquid Crystals
• Scalar ${\varphi }^4$ field theory for active-particle phase separation
• Active nematics on a substrate: giant number fluctuations and long-time tails
• Cluster phases and bubbly phase separation in active fluids: Reversal of the Ostwald process
• Flow-induced phase separation of active particles is controlled by boundary conditions
• Active Model H: Scalar Active Matter in a Momentum-Conserving Fluid
• Origins and diagnostics of the nonequilibrium character of active systems
• Activating membranes
• Hydrodynamically interrupted droplet growth in scalar active matter
• A two-sphere model for bacteria swimming near solid surfaces
• Active phase separation: new phenomenology from non-equilibrium physics
• Screening, Hyperuniformity, and Instability in the Sedimentation of Irregular Objects
• Long-range fluctuation-induced forces in driven electrolytes
• Controlling cell motion and microscale flow with polarized light fields
• Re-enterant efficiency of phototaxis in Chlamydomonas reinhardtii cells
• Universal properties of repulsive self-propelled particles and attractive driven particles
• The effect of inter-particle hydrodynamic and magnetic interactions in a magnetorheological fluid
• Current fluctuations across a nanopore
• Anomalous Diffusion in Driven Electrolytes due to Hydrodynamic Fluctuations