Results 51 to 60 of about 81 (74)

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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Dominions in quasivarieties of metabelian groups

Siberian Mathematical Journal, 2010
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Quasivarieties generated by partially commutative groups

Siberian Mathematical Journal, 2013
A free partially commutative group is a group of the form \(F=\langle X\mid x_ix_j=x_jx_i\) if \((x_i,x_j)\in E\rangle\), where \(E\) is the set of edges of a given graph. If we add the identity \([[x,y],[u,v]]=1\) to the defining relations of \(F\) we obtain a free partially commutative metabelian group.
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Minimal quasivarieties of endographs

Mathematical Notes, 1992
Let \(\langle A; p,f\rangle\) be an algebraic system containing a binary predicate symbol \(p\) and a unary function symbol \(f\). An algebraic system \(\langle A; p,f\rangle\) is said to be an endograph if it satisfies the quasi-identity \((\forall x)(\forall y)(p(x,y)\to p(f(x),f(y)))\).
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Maximal quasivarieties of groups

Algebra and Logic, 1998
Lattices \(L_q(qG)\) of quasivarieties contained in the quasivariety \(qG\), generated by a polycyclic-by-finite group \(G\), are considered. It is proved that every lattice under consideration contains finitely many coatoms (i.e. proper maximal elements) and that each of its elements distinct from \(qG\) is contained in some coatom.
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