A1 Refereed original research article in a scientific journal

Avoiding abelian powers cyclically




AuthorsPeltomäki Jarkko, Whiteland Markus A.

PublisherElsevier

Publication year2020

JournalAdvances in Applied Mathematics

Article number102095

Volume121

Number of pages22

ISSN0196-8858

eISSN1090-2074

DOIhttps://doi.org/10.1016/j.aam.2020.102095

Self-archived copy’s web addresshttps://research.utu.fi/converis/portal/detail/Publication/49631547


Abstract

We study a new notion of cyclic avoidance of abelian powers. A finite word $w$ avoids abelian $N$-powers cyclically if for each abelian $N$-power of period $m$ occurring in the infinite word $w^\omega$, we have $m \geq |w|$. Let $\mathcal{A}(k)$ be the least integer $N$ such that for all $n$ there exists a word of length $n$ over a $k$-letter alphabet that avoids abelian $N$-powers cyclically. Let $\mathcal{A}_\infty(k)$ be the least integer $N$ such that there exist arbitrarily long words over a $k$-letter alphabet that avoid abelian $N$-powers cyclically.

We prove that $5 \leq \mathcal{A}(2) \leq 8$, $3 \leq \mathcal{A}(3) \leq 4$, $2 \leq \mathcal{A}(4) \leq 3$, and $\mathcal{A}(k) = 2$ for $k \geq 5$. Moreover, we show that $\mathcal{A}_\infty(2) = 4$, $\mathcal{A}_\infty(3) = 3$, and $\mathcal{A}_\infty(4) = 2$.


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Last updated on 2024-26-11 at 22:09