theorem curvature_lemma (_hJ : 2 ≤ J) {ρ : ℝ} (_hρ : ρ < 1) {c : ℝ} (_hc : 0 < c) : cesPrincipalCurvature J ρ c = (1 - ρ) / (c * Real.sqrt ↑J) := by rfl
thesis/CESProofs/Foundations/Hessian.lean:203
Gradient and Hessian of CES at the symmetric point.