theorem cesPotential_zero_friction (q : ℝ) (p ε : Fin J → ℝ) : cesPotential J q 0 p ε = ∑ j : Fin J, p j * ε j := by simp [cesPotential]
thesis/CESProofs/Potential/CESPotential.lean:99
Theorem 3: CES Potential Uniqueness (Paper 2, Section 3.2)