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arXiv · 2605.21275

An Improved Upper Bound for the Dirichlet Spectrum in Diophantine Approximation

Zixuan Peng·Siyuan Wang·Ethan Wang
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Abstract

We study the continuous part of the Dirichlet spectrum $\mathbb{D}$ and improve the best previously published upper bound for the ray-origin constant $\delta$. Building on and refining V. A. Ivanov's approach, we introduce a Cantor-type set $F_4^*$ defined by certain restrictions on partial quotients. For its thickness, we prove $\tau(\log(F_4^*))>1$, and apply sum-set results for Cantor sets to prove that the set $F_4^* \cdot F_4^*$ is an interval. Finally, we establish a new upper bound $\delta\le \frac{111(397+\sqrt{26565})}{65522}\approx0.94866$.

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Zixuan Peng, Siyuan Wang, Ethan Wang. 2026-05-20. An Improved Upper Bound for the Dirichlet Spectrum in Diophantine Approximation. https://arxiv.org/abs/2605.21275

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