Chirikov Standard Map

Area-preserving chaos on a torus. KAM tori persist for small K, dissolve into chaos above K ≈ 0.9716 — the "last KAM torus"

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KAM threshold: K* ≈ 0.9716
Below: closed invariant curves
Above: global chaos
Map: θₙ₊₁ = θₙ + pₙ₊₁
pₙ₊₁ = pₙ + K·sin(θₙ)
(mod 2π)

K=0: Integrable — pure rotation, every orbit is periodic or quasi-periodic.

K small: KAM theorem — most invariant tori survive, perturbed slightly.

K≈0.97: Last KAM torus (Greene's criterion) — the "critical" golden-mean orbit breaks.

K large: Fully developed chaos — orbits fill the torus ergodically.

Click on the canvas to seed individual orbits and watch their trajectories.