On uniform polynomial approximation

Abstract

Let $n$ be a positive integer and $ξ$ a transcendental real number. We are interested in bounding from above the uniform exponent of polynomial approximation $\widehatω_n(ξ)$. Davenport and Schmidt's original 1969 inequality $\widehatω_n(ξ)\leq 2n-1$ was improved recently, and the best upper bound known to date is $2n-2$ for each $n\geq 10$. In this paper, we develop new techniques leading us to the improved upper bound $2n-\frac{1}{3}n^{1/3}+\mathcal{O}(1)$.