Eilenberg correspondence for Stone recognition

Fuente: arXiv
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Autores principales: Almeida, Jorge, Klíma, Ondřej
Formato: Preprint
Publicado: 2025
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author Almeida, Jorge
Klíma, Ondřej
author_facet Almeida, Jorge
Klíma, Ondřej
contents We develop and explore the idea of recognition of languages (in the general sense of subsets of topological algebras) as preimages of clopen sets under continuous homomorphisms into Stone topological algebras. We obtain an Eilenberg correspondence between varieties of languages and varieties of ordered Stone topological algebras and a Birkhoff/Reiterman-type theorem showing that the latter may me defined by certain pseudo-inequalities. In the case of classical formal languages, of words over a finite alphabet, we also show how this extended framework goes beyond the class of regular languages by working with Stone completions of minimal automata, viewed as unary algebras. This leads to a general method for showing that a language does not belong to a variety of languages, expressed in terms of sequences of pairs of words, which is illustrated when the class consists of all finite intersections of context-free languages.
format Preprint
id arxiv_https___arxiv_org_abs_2507_00409
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Eilenberg correspondence for Stone recognition
Almeida, Jorge
Klíma, Ondřej
Formal Languages and Automata Theory
46H05 (Primary) 06E15, 08A62 (Secondary)
We develop and explore the idea of recognition of languages (in the general sense of subsets of topological algebras) as preimages of clopen sets under continuous homomorphisms into Stone topological algebras. We obtain an Eilenberg correspondence between varieties of languages and varieties of ordered Stone topological algebras and a Birkhoff/Reiterman-type theorem showing that the latter may me defined by certain pseudo-inequalities. In the case of classical formal languages, of words over a finite alphabet, we also show how this extended framework goes beyond the class of regular languages by working with Stone completions of minimal automata, viewed as unary algebras. This leads to a general method for showing that a language does not belong to a variety of languages, expressed in terms of sequences of pairs of words, which is illustrated when the class consists of all finite intersections of context-free languages.
title Eilenberg correspondence for Stone recognition
topic Formal Languages and Automata Theory
46H05 (Primary) 06E15, 08A62 (Secondary)
url https://arxiv.org/abs/2507.00409