Coexisting synchrony and incoherence in nonlocally coupled oscillators
A chimera state is a counterintuitive solution of a ring of identical phase oscillators with nonlocal coupling: dθ_i/dt = ω + (K/2R)Σ|i-j|≤R sin(θ_j - θ_i - α). Despite identical oscillators and symmetric coupling, the system spontaneously breaks into synchronized and incoherent regions. Discovered by Kuramoto & Battogtokh (2002), chimeras were initially considered paradoxical; they have since been observed experimentally in optical, chemical, and mechanical systems.