Speaker
Description
More than two decades ago it was shown [PRL 89, 058101 (2002)] that flocks in fluids are unstable at least in the viscous limit. This instability of uniaxial orientational order in bulk active fluids is an inescapable consequence of the conservation of total mass and momentum. In this talk, I will use the fluctuating, broken-symmetry hydrodynamic framework for internally driven (i.e., active) systems to show that the very activity that conspires with conservation laws to destroy bulk nematic or polar ordering can instead promote it, with radically suppressed fluctuations, in a layer of active fluid in contact with a solid or fluid medium. These escapes from the bulk instability and active stabilisation of uniaxial order via dynamical, nonequilibrium analogues of the Anderson-Higgs mechanism, would be impossible in equilibrium systems in which the existence of order and all equal-time correlators are independent of dynamics and the presence or absence of conservation laws.
