Logical isomorphism and logical limit laws for small permutation classes and regular languages
Abstract
In this paper we show that for each small permutation class ℱ there exists a regular language LF such that the monadic second-order TOTO logic on ℱ is isomorphic to classical monadic second-order logic on LF. Thanks to the fact that regular languages are closed under monadic second-order restrictions this shows that many subsets of ℱ have a well-behaved structure. In particular, this allows us to show that random permutations from any small permutation class satisfies convergence laws for both first-order logic and monadic second-order logic. In the latter case, the law is modular. Our proofs introduce a way of using the automaton description of regular languages to prove properties of generating functions which may be of independent interest. Potential applications include first-order limit laws for random words in some regular languages.
Related
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- Permutation classes need not have proper growth rates
BibTeX
@misc{markstrom2026logical,
title = {{Logical isomorphism and logical limit laws for small permutation classes and regular languages}},
author = {Klas Markström and Eero Räty},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.22218},
eprint = {2610.22218},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.22218},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Logical isomorphism and logical limit laws for small permutation classes and regular languages
AU - Klas Markström
AU - Eero Räty
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.22218
UR - https://arxiv.org/abs/2610.22218
AB - In this paper we show that for each small permutation class ℱ there exists a regular language L_F such that the monadic second-order TOTO logic on ℱ is isomorphic to classical monadic second-order logic on L_F. Thanks to the fact that regular languages are closed under monadic second-order restrictions this shows that many subsets of ℱ have a well-behaved structure. In particular, this allows us to show that random permutations from any small permutation class satisfies convergence laws for both first-order logic and monadic second-order logic. In the latter case, the law is modular. Our proofs introduce a way of using the automaton description of regular languages to prove properties of generating functions which may be of independent interest. Potential applications include first-order limit laws for random words in some regular languages.
ER -