Visibly Pushdown Languages in Groups

Fuente: arXiv
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Main Authors: Ciobanu, Laura, Turaev, Daniel
Format: Preprint
Published: 2026
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author Ciobanu, Laura
Turaev, Daniel
author_facet Ciobanu, Laura
Turaev, Daniel
contents In this paper we explore the connections between the class of Visibly Pushdown Languages ($\mathbf{VPL}$) and the natural sets of words one can associate to a finitely generated group. We show that the word problem of a finitely generated group is $\mathbf{VPL}$ exactly when the group is finite. We also show that free reduction does not preserve $\mathbf{VPL}$, and that finding solutions to equations in a free group with $\mathbf{VPL}$ constraints (as reduced words) is undecidable. We explore the structure of sets whose full preimage is $\mathbf{VPL}$, showing these are often recognisable sets. We conjecture that, in any group, this class is precisely the recognisable sets.
format Preprint
id arxiv_https___arxiv_org_abs_2604_22375
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Visibly Pushdown Languages in Groups
Ciobanu, Laura
Turaev, Daniel
Group Theory
Formal Languages and Automata Theory
In this paper we explore the connections between the class of Visibly Pushdown Languages ($\mathbf{VPL}$) and the natural sets of words one can associate to a finitely generated group. We show that the word problem of a finitely generated group is $\mathbf{VPL}$ exactly when the group is finite. We also show that free reduction does not preserve $\mathbf{VPL}$, and that finding solutions to equations in a free group with $\mathbf{VPL}$ constraints (as reduced words) is undecidable. We explore the structure of sets whose full preimage is $\mathbf{VPL}$, showing these are often recognisable sets. We conjecture that, in any group, this class is precisely the recognisable sets.
title Visibly Pushdown Languages in Groups
topic Group Theory
Formal Languages and Automata Theory
url https://arxiv.org/abs/2604.22375