40 research outputs found
Entropy production fluctuations encode collective behavior in active matter
We derive a general lower bound on distributions of entropy production in
interacting active matter systems. The bound is tight in the limit that
interparticle correlations are small and short-ranged, which we explore in four
canonical active matter models. In all models studied, the bound is weak where
collective fluctuations result in long-ranged correlations, which subsequently
links the locations of phase transitions to enhanced entropy production
fluctuations. We develop a theory for the onset of enhanced fluctuations and
relate it to specific phase transitions in active Brownian particles. We also
derive optimal control forces that realize the dynamics necessary to tune
dissipation and manipulate the system between phases. In so doing, we uncover a
general relationship between entropy production and pattern formation in active
matter, as well as ways of controlling it
Low Mach number fluctuating hydrodynamics model for ionic liquids
We present a new mesoscale model for ionic liquids based on a low Mach number fluctuating hydrodynamics formulation for multicomponent charged species. The low Mach number approach eliminates sound waves from the fully compressible equations leading to a computationally efficient incompressible formulation. The model uses a Gibbs free-energy functional that includes enthalpy of mixing, interfacial energy, and electrostatic contributions. These lead to a new fourth-order term in the mass equations and a reversible stress in the momentum equations. We calibrate our model using parameters for [DMPI+][F6P-], an extensively studied room temperature ionic liquid (RTIL), and numerically demonstrate the formation of mesoscopic structuring at equilibrium in two and three dimensions. In simulations with electrode boundaries the measured double-layer capacitance decreases with voltage, in agreement with theoretical predictions and experimental measurements for RTILs. Finally, we present a shear electroosmosis example to demonstrate that the methodology can be used to model electrokinetic flows