A continuum field theory for phase-separating suspensions of two non-reciprocally coupled species, coupling the non-reciprocal Cahn-Hilliard concentration dynamics to a momentum-conserving Stokes fluid. Long-range hydrodynamic interactions, absent in dry (mobility-only) models, qualitatively reshape the phase diagram: they shift the onset of the oscillatory (traveling-wave) instability driven by non-reciprocity and select the emergent length and time scales of the chasing bands and traveling states. The model shows how conserved-order-parameter dynamics, non-reciprocal cross-coupling, and low-Reynolds-number hydrodynamics jointly govern pattern formation in active mixtures.
Builds the hydrodynamic non-reciprocal Cahn-Hilliard (h-NRCH) model to ask how self-generated fluid flows affect the travelling waves and emergent polar order that arise when two conserved density fi…