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Difference of irrationality measure functions

Number Theory 2023-08-24 v2

Abstract

For an irrational number αR\alpha\in\mathbb{R} we consider its irrationality measure function ψα(x)=min1qx,qZqα. \psi_\alpha(x) = \min_{1\le q\le x,\, q\in\mathbb{Z}} \| q\alpha \|. It is known for all irrational numbers α\alpha and β\beta satisfying α±β∉Z\alpha\pm\beta\not\in\mathbb{Z}, there exist arbitrary large values of tt with \begin{equation*} | \psi_\alpha(t) - \psi_\beta(t) | \geqslant \left( \sqrt{\tau} - 1\right) \cdot \min( \psi_\alpha(t), \psi_\beta(t) ), \end{equation*} where τ=5+12\tau = \frac{\sqrt{5} + 1}{2} and this result is optimal for certain numbers equivalent to τ\tau. Here we prove that for all irrational numbers α\alpha and β\beta, satisfying α±β∉Z\alpha\pm\beta\not\in\mathbb{Z}, such that at least one of them is not equivalent to τ\tau, there exist arbitrary large values of tt with ψα(t)ψβ(t)(2+11)min(ψα(t),ψβ(t)). | \psi_\alpha(t) - \psi_\beta(t) | \geqslant (\sqrt{\sqrt2+1}-1)\cdot \min( \psi_\alpha(t), \psi_\beta(t) ). Moreover, we show that the constant on the right-hand side is optimal.

Cite

@article{arxiv.2305.10264,
  title  = {Difference of irrationality measure functions},
  author = {Viktoria Rudykh and Nikita Shulga},
  journal= {arXiv preprint arXiv:2305.10264},
  year   = {2023}
}

Comments

15 pages, 1 figure. Comments will be appreciated

R2 v1 2026-06-28T10:37:10.298Z