English

Topological invariants for words of linear factor complexity

Formal Languages and Automata Theory 2022-05-12 v2

Abstract

Given a finite alphabet Σ\Sigma and a right-infinite word ww over the alphabet Σ\Sigma, we construct a topological space Rec(w){\rm Rec}(w) consisting of all right-infinite recurrent words whose factors are all factors of ww, where we work up to an equivalence in which two words are equivalent if they have the exact same set of factors (finite contiguous subwords). We show that Rec(w){\rm Rec}(w) can be endowed with a natural topology and we show that if ww is word of linear factor complexity then Rec(w){\rm Rec}(w) is a finite topological space. In addition, we note that there are examples which show that if f:NNf:\mathbb{N}\to \mathbb{N} is a function that tends to infinity as nn\to \infty then there is a word whose factor complexity function is O(nf(n)){\rm O}(nf(n)) such that Rec(w){\rm Rec}(w) is an infinite set. Finally, we pose a realization problem: which finite topological spaces can arise as Rec(w){\rm Rec}(w) for a word of linear factor complexity?

Keywords

Cite

@article{arxiv.2202.00643,
  title  = {Topological invariants for words of linear factor complexity},
  author = {Jason Bell},
  journal= {arXiv preprint arXiv:2202.00643},
  year   = {2022}
}

Comments

14 pages

R2 v1 2026-06-24T09:14:13.116Z