Results 41 to 50 of about 74 (68)

SUBFUNCTORS ASSOCIATED WITH QUASIVARIETIES

1984
Quasivarieties of algebras are characterized as SP-classes closed under a certain construction of directed unions of congruences.
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Quasivariety of special jordan algebras

Algebra and Logic, 1983
It is well known that the class of all special Jordan algebras does not form a variety of algebras, but it is not difficult to see that this class forms a quasivariety of algebras. The natural question then arises whether this quasivariety can be defined by a finite number of quasi- identities.
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Quasivarieties of Graphs and Independent Axiomatizability

Siberian Advances in Mathematics, 2018
Summary: In the present article, we continue to study the complexity of the lattice of quasivarieties of graphs. For every quasivariety \(K\) of graphs that contains a non-bipartite graph, we find a subquasivariety \(K'\subset K\) such that there exist \(2^{\omega}\) subquasivarieties \(K'' \in L_q(K')\) without covers (hence, without independent bases
Kravchenko, A. V., Yakovlev, A. V.
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Quasivarieties of graphs

Siberian Mathematical Journal, 1994
By a graph we mean a model of a binary predicate \(\rho(x,y)\). Many well-known properties of binary relations, such as reflexivity, symmetry, antisymmetry, transitivity, etc., are written down by means of quasiidentities. Such important classes of graphs as the class of all partial orders, the class of models of an equivalence relation, the class of ...
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Categorical quasivarieties revisited

Algebra Universalis, 1984
We offer simple new characterizations of \(\omega\)-categorical quasivarieties and varieties of countable type. Our arguments are distinguished by the absence of any sophisticated model theory. In the beginning we use some very basic model theory, but after that we find that combinatorial reasoning about finite sets and elementary algebraic arguments ...
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Quasivarieties with Definable Relative Principal Subcongruences

Studia Logica, 2009
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Nurakunov, A. M., Stronkowski, M. M.
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$$\mathcal{Q}$$ -Universal Quasivarieties of Graphs

Algebra and Logic, 2002
It is proved that a quasivariety \(K\) of undirected graphs without loops is \(\mathcal Q\)-universal if and only if \(K\) contains some non-bipartite graph.
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Structure of quasivariety lattices. I. Independent axiomatizability

Algebra i logika, 2017
A quasivariety \(K\) has an \(\omega \)-independent quasi-equational basis in a quasivariety \(M\) if there are a basis \(\Phi \) of \(K\) in \(M\) and a partition \(\Phi =\cup_ ...
Kravchenko, A. V., Nurakunov, A. M., Schwidefsky, M. V.   +2 more
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Quasivarieties of Algebras

2001
This chapter plays a twofold role in the book. Firstly, the chapter surveys basic facts about quasivarieties of algebras. These facts are widely utilised in the subsequent chapters devoted to algebraizable logics. Secondly, the chapter shows how the methods initially elaborated for protoalgebraic sentential logics in the first part can be also applied ...
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Quasivariety Lattices of Pointed Abelian Groups

Algebra and Logic, 2014
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