Hamilton-Jacobi · Action Surface
unseel.com · ∂S/∂t + H(q, ∂S/∂q) = 0 · wavefronts & rays
Phase S/ℏ
p = ∂S/∂q
beat
Action surface S(q,t)
Wavefronts (constant S)
Characteristics = trajectories
Unseel.com · Hamilton-Jacobi