Hénon-Heiles: Poincaré Section

KAM tori at low energy → chaotic sea at high energy

H = ½(ẋ²+ẏ²+x²+y²) + x²y − y³/3. Section: y=0, ẏ>0. At E<1/12: invariant KAM tori. At E→1/6: chaos fills section. λ_c ≈ 1/6 (escape energy).