theorem prudence_locking [NeZero J]
(x : Fin J → ℝ) (hx : ∀ j, 0 < x j) (ρ : ℝ) :
-- (i) kappa_3 is the derivative of kappa_2
HasDerivAt (fun p => escortCumulant2 x p) (escortCumulant3 x ρ) ρ ∧
-- (ii) Both vanish at symmetry
(∀ c : ℝ, 0 < c →
escortCumulant2 (fun _ : Fin J => c) ρ = 0 ∧
escortCumulant3 (fun _ : Fin J => c) ρ = 0) :=
⟨cumulant3_is_derivative_of_variance x hx ρ,
fun _ hc => ⟨escortCumulant2_zero_at_symmetry hc ρ,
escortCumulant3_zero_at_symmetry hc ρ⟩⟩The Cumulant Tower: Higher-Order Bridges Between CES and Escort Statistics