Results 21 to 30 of about 101 (90)

Algebraic Theories of Quasivarieties

Journal of Algebra, 1998
By the theory of a locally finitely presentable category \(\mathcal K\) is meant the dual \(\text{Th}(\mathcal K)\) of the subcategory of finitely presentable objects. The authors characterize the theories of (many-sorted, finitary) (a) quasivarieties and (b) Horn classes.
Adámek, Jiřı́, Porst, Hans-E
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Remarks on an algebraic semantics for paraconsistent Nelson's logic

Manuscrito, 2011
In the paper Busaniche and Cignoli (2009) we presented a quasivariety of commutative residuated lattices, called NPc-lattices, that serves as an algebraic semantics for paraconsistent Nelson's logic.
Manuela Busaniche, Roberto Cignoli
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Note on quasivarieties generated by finite pointed abelian groups

Open Mathematics
We prove that a finite pointed abelian group generates a finitely axiomatizable variety that has a finite quasivariety lattice. As a consequence, we obtain that a quasivariety generated by a finite pointed abelian group has a finite basis of quasi ...
Basheyeva Ainur, Lutsak Svetlana
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How to Sketch Quasivarieties

Journal of Algebra, 1996
The author describes a class of sketches, ``separated limit sketches'', such that quasivarieties of finitary algebras are precisely the categories sketchable by separated finite-limit sketches. This result has an extension with ``finitary'' replaced by a cardinal parameter.
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Criterion for a formula-definable quasivariety

Қарағанды университетінің хабаршысы. Математика сериясы
In this paper, we study classes of models of a first-order language L with a countable signature σ. For a model A, let Th(A) denote the set of all sentences of L that are true in A, called the elementary type of A.
M.I. Bekenov, A. Mamyraly, A. Kassatova, A. Kabidenov   +3 more
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Decidable quasivarieties of p‐algebras

Mathematical Logic Quarterly
Abstract We show that for quasivarieties of p‐algebras the properties of (i) having decidable first‐order theory and (ii) having decidable first‐order theory of the finite members, coincide. The only two quasivarieties with these properties are the trivial variety and the variety of Boolean algebras.
Tomasz Kowalski, Katarzyna Słomczyńska
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Localizations of varieties and quasivarieties

Journal of Pure and Applied Algebra, 2000
It is well known that varieties (= monadic categories over sets) are nothing but exact categories having a regular projective regular generator with copowers. It is also well known that quasivarieties (= regular epireflective full subcategories of varieties) are nothing but regular categories having coequalizers of equivalence relations and a regular ...
PEDICCHIO, MARIA CRISTINA, J. ROSICKY
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The Operator Ln on Quasivarieties of Universal Algebras

Siberian Mathematical Journal, 2019
Let $n$ be an arbitrary natural number and let $M$ be a class of universal algebras. Denote by $L_n(M)$ the class of algebras $G$ such that, for every $n$-generated subalgebra $A$ of $G$, the coset $a/R$ $(a\in A)$ modulo the least congruence $R$ including $A\times A$ is an algebra in $M$.
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The logic induced by effect algebras. [PDF]

Soft comput, 2020
Chajda I, Halaš R, Länger H.
europepmc   +1 more source

Sequent calculi and quasivarieties

Reports Math. Log., 2000
Summary: We discuss relatively point-regular quasivarieties related in some special sense to sequent calculi. We show that the free algebra in such a quasivariety is Fregean iff in the sequent calculus the so-called symmetric contraction rules are admissible. In the presence of the fusion connective this is equivalent to having contraction.
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