Periodica Mathematica Hungarica

, Volume 75, Issue 2, pp 221–243

# Counting exceptional points for rational numbers associated to the Fibonacci sequence

Article

## Abstract

If $$\alpha$$ is a non-zero algebraic number, we let $$m(\alpha )$$ denote the Mahler measure of the minimal polynomial of $$\alpha$$ over $$\mathbb Z$$. A series of articles by Dubickas and Smyth, and later by the author, develop a modified version of the Mahler measure called the t-metric Mahler measure, denoted $$m_t(\alpha )$$. For fixed $$\alpha \in \overline{\mathbb Q}$$, the map $$t\mapsto m_t(\alpha )$$ is continuous, and moreover, is infinitely differentiable at all but finitely many points, called exceptional points for $$\alpha$$. It remains open to determine whether there is a sequence of elements $$\alpha _n\in \overline{\mathbb Q}$$ such that the number of exceptional points for $$\alpha _n$$ tends to $$\infty$$ as $$n\rightarrow \infty$$. We utilize a connection with the Fibonacci sequence to formulate a conjecture on the t-metric Mahler measures. If the conjecture is true, we prove that it is best possible and that it implies the existence of rational numbers with as many exceptional points as we like. Finally, with some computational assistance, we resolve various special cases of the conjecture that constitute improvements to earlier results.

## Keywords

Mahler measure Metric Mahler measure Fibonacci numbers

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