English

Palindromic Length and Reduction of Powers

Combinatorics 2022-07-19 v1 Discrete Mathematics

Abstract

Given a nonempty finite word vv, let PL(v)PL(v) be the palindromic length of vv; it means the minimal number of palindromes whose concatenation is equal to vv. Let vRv^R denote the reversal of vv. Given a finite or infinite word yy, let Fac(y)Fac(y) denote the set of all finite factors of yy and let maxPL(y)=max{PL(t)tFac(y)}maxPL(y)=\max\{PL(t)\mid t\in Fac(y)\}. Let xx be an infinite non-ultimately periodic word with maxPL(x)=k<maxPL(x)=k<\infty and let uFac(x)u\in Fac(x) be a primitive nonempty factor such that u5u^5 is recurrent in xx. Let Ψ(x,u)={tFac(x)u,uR∉Fac(t)}\mbox.\Psi(x,u)=\{t\in Fac(x)\mid u,u^R\not\in Fac(t)\}\mbox{.} We construct an infinite non-ultimately periodic word x\overline x such that u5,(uR)5∉Fac(x)u^5, (u^R)^5\not\in Fac(\overline x), Ψ(x,u)Fac(x)\Psi(x,u)\subseteq Fac(\overline x), and maxPL(x)3k3maxPL(\overline x)\leq 3k^3. Less formally said, we show how to reduce the powers of uu and uRu^R in xx in such a way that the palindromic length remains bounded.

Keywords

Cite

@article{arxiv.2103.14609,
  title  = {Palindromic Length and Reduction of Powers},
  author = {Josef Rukavicka},
  journal= {arXiv preprint arXiv:2103.14609},
  year   = {2022}
}
R2 v1 2026-06-24T00:35:44.894Z