Interaction of in-phase and anti-phase synchronies in a coupled compartment-bulk diffusion model at a double Hopf bifurcation

We study a model of chemical oscillations in two identical compartments, coupled by a chemical signal diffusing and degrading in the 1D bulk medium between the compartments. The nonlinear compartment-bulk diffusion model consists of a coupled system of ordinary and partial differential equations. Previous numerical work on this system reveals the presence of two modes of synchronized oscillations, in-phase and anti-phase, which arise from Hopf bifurcations of the unique steady state of the system. The coincidence of the two Hopf bifurcations indicates a double Hopf bifurcation point. We use centre manifold and normal form theory to reduce the local dynamics of the model system to a system of two amplitude equations, which determines the patterns of Hopf bifurcation and stability of the two modes near the double Hopf point. In the case of bistability, the stable manifold of an unstable invariant torus forms the boundary between the basins of attraction of the stable in-phase and anti-phase modes. Numerical simulations support these predictions.