On ‘‘Simple’’ Undecidable Fragments of the Positive Theory of a Free Semigroup
Valery Georgievich Durnev, О. В. Зеткина, Алена Игоревна Зеткина · Lobachevskii Journal of Mathematics · 2020
Abstract We prove algorithmic undecidability of ‘‘simple’’ (with respect to the quantifier-prefix and the quantifier-free part of the formulas) fragments of positive theories of finitely generated semigroups.