Hydrodynamic limit of an active-passive lattice gas

In this talk, the speaker discusses a model mixture of active (self-propelled) and passive (diffusive) particles with non-reciprocal effective interactions (i.e., forces that violate Newton's third law). The speaker derives the hydrodynamic PDE limit for the particle densities, which is not a Wasserstein gradient flow of any free energy, consistent with the microscopic model exhibiting non-equilibrium steady states. The talk explores the emergence of collective behaviour, including phase separation and dynamical (travelling) steady states.

Joint work with Clément Erignoux, Rob Jack and James Mason.