In mathematics, the Landau–Kolmogorov inequality, named after Edmund Landau and Andrey Kolmogorov, is the following family of interpolation inequalities between different derivatives of a function f defined on a subset T of the real numbers: ‖ f ‖ L ∞ ≤ C ‖ f ‖ L ∞ 1 − k / n ‖ f ‖ L ∞ k / n for 1 ≤ k < n. Wikipedia