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Algebra Logika, 2022 Volume 61, Number 6, Pages 766–783 (Mi al2741)

Generic complexity of word problem in some semigroups

A. N. Rybalov

Omsk Branch of Sobolev Institute of Mathematics, Siberian Branch of the Russian Academy of Sciences

Abstract: Generic algorithms decide problems on sets of almost all inputs, outputting an indefinite answer for other rare inputs. We will prove that the word problem is generically decidable in finitely generated semigroups $\mathfrak{S}$, for which there exists a congruence $\theta$ such that the semigroup $\mathfrak{S}/ \theta$ is an infinite residually finite monoid with cancellation property and decidable word problem. This generalizes the author' earlier result on generic decidability of the word problem in finitely presented semigroups that remain infinite when adding commutativity and cancelling properties. Examples of such semigroups are one-relator semigroups as well as so-called balanced semigroups, for which generic decidability of the word problem has been proved by Won. In particular, balanced are Tseitin and Makanin's classical semigroups with undecidable word problem.

Keywords: word problem, generic decidability, finitely generated semigroup.

UDC: 510.643

Received: 29.04.2022
Revised: 13.10.2023

DOI: 10.33048/alglog.2022.61.606


 English version:
Algebra and Logic, 2022, 61:6, 524–536


© Steklov Math. Inst. of RAS, 2026