Fractal geometry without chaos — Grebogi-Ott-Pelikan 1984
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Lyapunov λ ≈ —Fractal dim ≈ —Mode: SNA
A strange nonchaotic attractor (SNA) has fractal geometry — like a chaotic attractor — but negative Lyapunov exponents, meaning nearby trajectories do NOT diverge exponentially. It lives in the "between" territory: quasiperiodically forced, geometrically complex, yet predictable. Discovered by Grebogi, Ott, and Pelikan in 1984. The phase θ advances by the golden ratio φ each step, ensuring quasiperiodic forcing that cannot lock onto any rational resonance.