English

Avoiding abelian powers cyclically

Formal Languages and Automata Theory 2020-11-04 v2

Abstract

We study a new notion of cyclic avoidance of abelian powers. A finite word ww avoids abelian NN-powers cyclically if for each abelian NN-power of period mm occurring in the infinite word wωw^\omega, we have mwm \geq |w|. Let A(k)\mathcal{A}(k) be the least integer NN such that for all nn there exists a word of length nn over a kk-letter alphabet that avoids abelian NN-powers cyclically. Let A(k)\mathcal{A}_\infty(k) be the least integer NN such that there exist arbitrarily long words over a kk-letter alphabet that avoid abelian NN-powers cyclically. We prove that 5A(2)85 \leq \mathcal{A}(2) \leq 8, 3A(3)43 \leq \mathcal{A}(3) \leq 4, 2A(4)32 \leq \mathcal{A}(4) \leq 3, and A(k)=2\mathcal{A}(k) = 2 for k5k \geq 5. Moreover, we show that A(2)=4\mathcal{A}_\infty(2) = 4, A(3)=3\mathcal{A}_\infty(3) = 3, and A(4)=2\mathcal{A}_\infty(4) = 2.

Cite

@article{arxiv.2006.06307,
  title  = {Avoiding abelian powers cyclically},
  author = {Jarkko Peltomäki and Markus A. Whiteland},
  journal= {arXiv preprint arXiv:2006.06307},
  year   = {2020}
}

Comments

18 pages, 1 figure