Additivity, density fluctuations, and nonequilibrium thermodynamics for active Brownian particles

摘要

Using an additivity property, we study particle-number fluctuations in asystem of interacting self-propelled particles, called active Brownianparticles (ABPs), which consists of repulsive disks with random self-propulsionvelocities. From a fluctuation-response relation - a direct consequence ofadditivity, we formulate a thermodynamic theory which captures the previouslyobserved features of nonequilibrium phase transition in the ABPs from ahomogeneous fluid phase to an inhomogeneous phase of coexisting gas and liquid.We substantiate the predictions of additivity by analytically calculating thesubsystem particle-number distributions in the homogeneous fluid phase awayfrom criticality where analytically obtained distributions are compatible withsimulations in the ABPs.