Morse Theory & Gradient Flow

Critical points · Morse index · Euler characteristic = Σ(−1)^λ

Surface

Critical Points:

Euler characteristic χ:
χ = Σ (−1)^λᵢ where λ = Morse index
Morse Lemma: Near a critical point, f ≈ −x₁²−⋯−x_λ²+x_{λ+1}²+⋯
Morse inequality: cₖ ≥ bₖ where bₖ = Betti numbers