Identical coupled oscillators spontaneously split into synchronized and incoherent clusters — a counterintuitive symmetry-breaking.
Kuramoto model with nonlocal coupling: dθᵢ/dt = ω + (σ/N) Σⱼ G(i-j) sin(θⱼ−θᵢ−α). Kuramoto (1984) + Battogtokh & Kuramoto (2002) discovered chimera states: partial synchronization in identical oscillators. Phase color: hue = phase angle. Incoherent (chaotic phases) vs coherent (locked phases) coexist spontaneously.