Coexistence of Uniform and Oscillatory States Resulting from Nonreciprocity and Conservation Laws

Employing a two-species Cahn-Hilliard model with nonreciprocal interactions, we show that the interplay of nonreciprocity and conservation laws results in the robust coexistence of uniform stationary and oscillatory phases as well as of uniform and crystalline phases. For nonequilibrium models with a spurious gradient dynamics structure, such coexistences between two or more nonequilibrium phases and resulting phase diagrams can, nevertheless, be predicted by a Maxwell double-tangent construction. This includes phases with sustained regular or irregular out-of-equilibrium dynamics as further corroborated by bifurcation studies and time simulations.