Abstract
Let \(\alpha \) and \(\beta \) be real numbers such that \(1\), \(\alpha \) and \(\beta \) are linearly independent over \(\mathbb {Q}\). A classical result of Dirichlet asserts that there are infinitely many triples of integers \((x_0,x_1,x_2)\) such that \(|x_0+\alpha x_1+\beta x_2| < \max \{|x_1|,|x_2|\}^{-2}\). In 1976, Schmidt asked what can be said under the restriction that \(x_1\) and \(x_2\) be positive. Upon denoting by \(\gamma \cong 1.618\) the golden ratio, he proved that there are triples \((x_0,x_1,x_2) \in \mathbb {Z}^3\) with \(x_1,x_2>0\) for which the product \(|x_0 + \alpha x_1 + \beta x_2| \max \{|x_1|,|x_2|\}^\gamma \) is arbitrarily small. Although Schmidt later conjectured that \(\gamma \) can be replaced by any number smaller than \(2\), Moshchevitin proved very recently that it cannot be replaced by a number larger than \(1.947\). In this paper, we present a construction of points \((1,\alpha ,\beta )\) showing that the result of Schmidt is in fact optimal. These points also possess strong additional Diophantine properties that are described in the paper.
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Communicated by C. Krattenthaler.
Work partially supported by NSERC.
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Roy, D. Diophantine approximation with sign constraints. Monatsh Math 173, 417–432 (2014). https://doi.org/10.1007/s00605-013-0584-0
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DOI: https://doi.org/10.1007/s00605-013-0584-0
Keywords
- Diophantine approximation
- Geometry of numbers
- Dirichlet’s theorem
- Linear forms
- Real numbers
- Positivity
- Angular domains
- Explicit construction