Two estimates concerning classical Diophantine approximation constants

In this paper we aim to prove two inequalities involving the classical approximation constants $w_{n}^{\prime}(ζ),\hat{w}_{n}^{\prime}(ζ)$ that stem from the simultaneous approximation problem $|ζ^{j}x-y_{j}|$, $1\leq j\leq n$, on the one side and the constants $w_{n}^{\ast}(ζ),\hat{w}_{n}^{\ast}(ζ)$ connected to approximation with algebraic numbers of degree $\leq n$ on the other side. We concretely prove $w_{n}^{\ast}(ζ)\hat{w}_{n}^{\prime}(ζ)\geq 1$ and $\hat{w}_{n}^{\ast}(ζ)w_{n}^{\prime}(ζ)\geq 1$. The first result is due to W. Schmidt, however our method of proving it allows to derive the other inequality as a dual result. Finally we will discuss estimates of $w_{n}^{\ast}(ζ), \hat{w}_{n}^{\ast}(ζ)$ uniformly in $ζ$ depending only on $n$ as an application.

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