  We study an oscillatory medium with a nonlinear global coupling that gives
rise to a harmonic mean-field oscillation with constant amplitude and
frequency. Two types of cluster states are found, each undergoing a
symmetry-breaking transition towards a related chimera state. We demonstrate
that the diffusional coupling is non-essential for these complex dynamics.
Furthermore, we investigate localized turbulence and discuss whether it can be
categorized as a chimera state.
