2024/08/07 by James Mason, Mason, James, Robert L. Jack +3 · 4 citations
Materials Science · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Classical mechanics #FOS: Physical sciences #Geology #Material Dynamics and Properties #Micro and Nano Robotics #Oceanography #Particle (ecology) #Physics #Reciprocal #Statistical Mechanics (cond-mat.stat-mech) #Statistical physics
paper · pdf · doi:10.48550/arxiv.2408.03932
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2024/08/07 · openalex created_date 2024/11/01 · openalex updated_date 2026/07/28
The formation of dynamical patterns is one of the most striking features of nonequilibrium physical systems. Recent work has shown that such patterns arise generically from forces that violate Newton's third law, known as nonreciprocal interactions. These nonequilibrium phenomena are challenging for modern theories. Here, we introduce a model mixture of active (self-propelled) and passive (diffusive) particles amenable to exact mathematical analysis. We exploit state-of-the-art methods to derive exact hydrodynamic equations for the particle densities, which reveal effective nonreciprocal couplings between the active and passive species. We study the resulting collective behavior, including the linear stability of homogeneous states and phase coexistence in large systems. This reveals a novel phase diagram with the spinodal associated with active phase separation protruding through the associated binodal, heralding the emergence of dynamical steady states. We analyze these states in the thermodynamic limit of large system size, showing, for example, that sharp interfaces may travel at finite velocities, but traveling phase-separated states are forbidden. The model's mathematical tractability enables precise new conclusions beyond those available by numerical simulation of particle models or field theories.