On the Landau-Kolmogorov inequality between $\| f' \|_{\infty}$, $\| f \|_{\infty}$ and $\| f''' \|_1$

Abstract

We solve the Landau-Kolmogorov problem on finding sharp additive inequalities that estimate $\| f' \|_{\infty}$ in terms of $\| f \|_{\infty}$ and $\| f''' \|_1$. Simultaneously we solve related problems of the best approximation of first order differentiation operator $D^1$ by linear bounded ones and the best recovery of operator $D^1$ on elements of a class given with error.

Keywords

• the Landau-Kolmogorov problem
• the Stechkin problem
• best recovery of operator
• modulus of continuity of operator