def isoquantDistSq (J : ℕ) (x y : Fin J → ℝ) (Fx Fy : ℝ) : ℝ := ∑ j : Fin J, (x j / Fx - y j / Fy) ^ 2
thesis/CESProofs/CurvatureRoles/Superadditivity.lean:31
Superadditivity of CES (Paper 1, Section 6):