On Bernstein's inequality for polynomials

Abstract

Bernstein's classical inequality asserts that given a trigonometric polynomial $T$ of degree $n\ge 1$, the sup-norm of the derivative of $T$ does not exceed $n$ times the sup-norm of $T$. We present various approaches to prove this inequality and some of its natural extensions/variants, especially when it comes to replacing the sup-norm with the $L^p-norm$.