MathSciDoc: An Archive for Mathematician ∫

We are studying the Diophantine exponent μ_{$n$,$l$}defined for integers 1≤$l$<$n$and a vector α∈ℝ^{$n$}by letting $$\mu_{n,l}=\sup\{\mu\geq0: 0 < \Vert\underline{x}\cdot\alpha\Vert<H(\underline{x})^{-\mu}\ \text{for infinitely many}\ \underline{x}\in\mathcal{C}_{n,l}\cap\mathbb{Z}^n\},$$ where $\cdot$ is the scalar product, $\|\cdot\|$ denotes the distance to the nearest integer and $\mathcal{C}_{n,l}$ is the generalised cone consisting of all vectors with the height attained among the first$l$coordinates. We show that the exponent takes all values in the interval [$l$+1,∞), with the value$n$attained for almost all α. We calculate the Hausdorff dimension of the set of vectors α with μ_{$n$,$l$}(α)=μ for μ≥$n$. Finally, letting$w$_{$n$}denote the exponent obtained by removing the restrictions on $\underline{x}$ , we show that there are vectors α for which the gaps in the increasing sequence μ_{$n$,1}(α)≤...≤μ_{$n$,$n$-1}(α)≤$w$_{$n$}(α) can be chosen to be arbitrary.

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