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The weak extension property and finite axiomatizability for quasivarieties

Wiesław Dziobiak, Miklós Maróti, Ralph McKenzie, Anvar Nurakunov (2009)

Fundamenta Mathematicae

We define and compare a selection of congruence properties of quasivarieties, including the relative congruence meet semi-distributivity, RSD(∧), and the weak extension property, WEP. We prove that if 𝒦 ⊆ ℒ ⊆ ℒ' are quasivarieties of finite signature, and ℒ' is finitely generated while 𝒦 ⊨ WEP, then 𝒦 is finitely axiomatizable relative to ℒ. We prove for any quasivariety 𝒦 that 𝒦 ⊨ RSD(∧) iff 𝒦 has pseudo-complemented congruence lattices and 𝒦 ⊨ WEP. Applying these results and other results...

The weak hereditary class of a variety

Wiktor Bartol, Francesc Rosselló (2006)

Czechoslovak Mathematical Journal

We study the weak hereditary class S w ( 𝒦 ) of all weak subalgebras of algebras in a total variety 𝒦 . We establish an algebraic characterization, in the sense of Birkhoff’s HSP theorem, and a syntactical characterization of these classes. We also consider the problem of when such a weak hereditary class is weak equational.

Théorie des magmoïdes

A. Arnold, M. Dauchet (1979)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

Théorie des magmoïdes (I)

A. Arnold, M. Dauchet (1978)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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