Geodesic Flow on Negative Curvature

Anosov system: exponential divergence of nearby geodesics, ergodic mixing on hyperbolic surface

Poincaré Upper Half-Plane (H²)

Geodesic Divergence (Anosov property)

Parameters

Lyapunov λ ≈ √|K|:
Mixing time:
|K|:
Entropy (KS):
Trajectories: 0
Hadamard-Perron theorem: geodesic flow on compact surface K<0 is Anosov — stable/unstable foliations split tangent space. Entropy h = √|K| (Liouville 1840s, rigorized by Anosov 1960s).