Robust Chaos in a Totally Symmetric Network of Four Phase Oscillators

The Kuramoto model and its generalizations are universal models of collective behavior in oscillatory networks. We provide conditions on the coupling function such that the Kuramoto system with four globally coupled identical oscillators has chaotic attractors: a pair of Lorenz attractors or a four-winged analog of the Lorenz attractor. The attractors emerge near the triple instability threshold of the splay-phase synchronization state of the oscillators. We provide theoretical arguments and verify numerically, based on the pseudohyperbolicity test, that the chaotic dynamics are robust with respect to small, e.g., time-dependent, perturbations of the system. The robust chaoticity should also be inherited by any network of weakly interacting systems with such attractors.