English

Note on dissecting power of regular languages

Formal Languages and Automata Theory 2025-09-16 v1

Abstract

Let c>1c>1 be a real constant. We say that a language LL is cc-\emph{constantly growing} if for every word uLu\in L there is a word vLv\in L with u<vc+u\vert u\vert<\vert v\vert\leq c+\vert u\vert. We say that a language LL is cc-\emph{geometrically growing} if for every word uLu\in L there is a word vLv\in L with u<vcu\vert u\vert<\vert v\vert\leq c\vert u\vert. Given a language LL, we say that LL is REGREG-\emph{dissectible} if there is a regular language RR such that LR=\vert L\setminus R\vert=\infty and LR=\vert L\cap R\vert=\infty. In 2013, it was shown that every cc-constantly growing language LL is REGREG-dissectible. In 2023, the following open question has been presented: "Is the family of geometrically growing languages REGREG-dissectible?" We construct a cc-geometrically growing language LL that is not REGREG-dissectible. Hence we answer negatively to the open question.

Cite

@article{arxiv.2310.14114,
  title  = {Note on dissecting power of regular languages},
  author = {Josef Rukavicka},
  journal= {arXiv preprint arXiv:2310.14114},
  year   = {2025}
}
R2 v1 2026-06-28T12:57:47.346Z