Chimera states in ensembles of excitable FitzHugh-Nagumo systems

An ensemble of nonlocally coupled excitable FitzHugh-Nagumo systems is studied. In the presence of noise the explored system can exhibit a special kind of chimera states called coherence-resonance chimera. As previously thought, noise plays principal role in forming these structures. It is shown in the present paper that these regimes appear because of the specific coupling between the elements. The action of coupling involves a spatial wave regime, which occurs in ensemble of excitable nodes even if the noise is switched off. In addition, a new chimera state is obtained in an excitable regime. This type of chimera has not been observed for excitable systems, especially in ensembles of FitzHugh-Nagumo ones. It is shown that the noise makes this chimera more stable near an Andronov-Hopf bifurcation.