Results 31 to 40 of about 439 (93)

Structure of quasivariety lattices. III. Finitely partitionable bases

Algebra i logika, 2020
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Kravchenko, A. V., Nurakunov, A. M., Schwidefsky, M. V.   +2 more
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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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Structure of quasivariety lattices. II. Undecidable problems

Algebra i logika, 2019
The paper provides sufficient conditions for a quasivariety \(\mathbf M\) to contain continuumly many subquasivarieties \(\mathbf K\) such that the membership problem for finitely presented structures in \(\mathbf M\) is undecidable in \(\mathbf K\), the finite membership problem is undecidable in \(\mathbf K\), the quasi-equational theory of \(\mathbf
Kravchenko, A. V., Nurakunov, A. M., Schwidefsky, M. V.   +2 more
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Algebraic atomistic lattices of quasivarieties

Algebra and Logic, 1997
Summary: The Gorbunov-Tumanov conjecture on the structure of lattices of quasivarieties is proven true for the case of algebraic lattices. Namely, for an algebraic atomistic lattice \(L\), the following conditions are equivalent: (1) \(L\) is represented as \(L_q(\mathcal K)\) for some algebraic quasivariety \(\mathcal K\); (2) \(L\) is represented as \
Adaricheva, K. V., Gorbunov, V. A., Dziobiak, W.   +2 more
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The lattice of quasivarieties of undirected graphs

Algebra Universalis, 2002
For a quasivariety \(\mathcal K\), let \(L(\mathcal K)\) denote the lattice of all quasivarieties contained in \(\mathcal K \). A quasivariety \(\mathcal K\) is said to be \(Q\)-universal if for any quasivariety \(\mathcal M\) of finite type, \(L(\mathcal M )\) is a homomorphic image of a sublattice of \(L(\mathcal K)\).
Adams, M. E., Dziobiak, W.
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Congruence properties of lattices of quasivarieties

Algebra and Logic, 1997
Summary: The congruence properties close to lower boundedness in the sense of McKenzie are treated. In particular, an affirmative answer is obtained to a known question as to whether finite lattices of quasivarieties are lower bounded in the case where quasivarieties are congruence-Noetherian and locally finite.
Adaricheva, K. V., Gorbunov, V. A., Dziobiak, W.   +2 more
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Complexity of Quasivariety Lattices

Algebra and Logic, 2015
A quasivariety \(\mathbf K\) is a class of algebraic systems closed under isomorphisms, subsystems, direct products, and ultraproducts. The quasivarieties contained in a quasivariety \(\mathbf K\) form a complete lattice \(\mathbf{Lq(K)}\) under inclusion. Quasivariety lattices might be highly complex. A measure of complexity is given by the notion of \
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UNREASONABLE LATTICES OF QUASIVARIETIES

International Journal of Algebra and Computation, 2012
A quasivariety is a universal Horn class of algebraic structures containing the trivial structure. The set [Formula: see text] of all subquasivarieties of a quasivariety [Formula: see text] forms a complete lattice under inclusion. A lattice isomorphic to [Formula: see text] for some quasivariety [Formula: see text] is called a lattice of ...
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Complexity of quasivariety lattices of pointed Abelian groups

Doklady Mathematics, 2012
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Imanaliev, M. I., Nurakunov, A. M.
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Quasivariety Lattices of Pointed Abelian Groups

Algebra and Logic, 2014
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