Counting Exceptional Points for Rational Numbers Associated to the Fibonacci Sequence

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 $\alpha \in \bar{\mathbb{Q}}$, the map $t\mapsto m_t(\alpha )$ is continuous, and moreover, is infinitely differentiable at all but finitely many points, called {\it exceptional points} for $\alpha$. It remains open to determine whether there is a sequence of elements ${\alpha }_n\in \bar{\mathbb{Q}}$ such that the number of exceptional points for ${\alpha }_n$ tends to $\infty$ as $n\to \infty$. 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 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.

References in corpus (6)

• An effective lower bound for the height of algebraic numbers
• The parametrized family of metric Mahler measures
• The $t$-metric Mahler measures of surds and rational numbers
• Metric Heights on an Abelian Group
• The infimum in the metric Mahler measure
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Cited by in corpus (2)

• A Polynomial Time Test to Detect Number with Many Exceptional Points
• Metric Mahler measures over number fields