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arXiv · 1806.02946

On spectrum of irrationality exponents of Mahler numbers

Dzmitry Badziahin
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Abstract

We consider Mahler functions $f(z)$ which solve the functional equation $f(z) = \frac{A(z)}{B(z)} f(z^d)$ where $\frac{A(z)}{B(z)}\in \mathbb{Q}(z)$ and $d\ge 2$ is integer. We prove that for any integer $b$ with $|b|\ge 2$ either $f(b)$ is rational or its irrationality exponent is rational. We also compute the exact value of the irrationality exponent for $f(b)$ as soon as the continued fraction for the corresponding Mahler function is known. This improves the result of Bugeaud, Han, Wei and Yao where only an upper bound for the irrationality exponent was provided.

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Dzmitry Badziahin. 2018-06-08. On spectrum of irrationality exponents of Mahler numbers. https://arxiv.org/abs/1806.02946

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