Construction of all strong homomorphisms of binary structures
Coverings in the lattice of quasivarieties of -groups.
Decompositions of homomorphisms
Does imply axiom of choice?
Dualities for Stone algebras, double Stone algebras, and relative Stone algebras
Duality for some free modes
The paper establishes a duality between a category of free subreducts of affine spaces and a corresponding category of generalized hypercubes with constants. This duality yields many others, in particular a duality between the category of (finitely generated) free barycentric algebras (simplices of real affine spaces) and a corresponding category of hypercubes with constants.
E-free objects and E-locality for completely regular semigroups.
Embedding semigroups in groups. A geometrical approach.
Embedding sums of cancellative modes into semimodules
A mode (idempotent and entropic algebra) is a Lallement sum of its cancellative submodes over a normal band if it has a congruence with a normal band quotient and cancellative congruence classes. We show that such a sum embeds as a subreduct into a semimodule over a certain ring, and discuss some consequences of this fact. The result generalizes a similar earlier result of the authors proved in the case when the normal band is a semilattice.
Equationally compact algebras (I)
Equationally compact algebras II
Equationally compact algebras (III)
Equations on the semidirect product of a finite semilattice by a finite commutative monoid.
Equimorphy in varieties of double Heyting algebras
We show that any finitely generated variety V of double Heyting algebras is finitely determined, meaning that for some finite cardinal n(V), any class ⊆ V consisting of algebras with pairwise isomorphic endomorphism monoids has fewer than n(V) pairwise non-isomorphic members. This result complements the earlier established fact of categorical universality of the variety of all double Heyting algebras, and contrasts with categorical results concerning finitely generated varieties of distributive...
Errata for the paper "Equationally compact algebras II" (Fundamenta Mathematica 61 (1968), pp. 271-281)
Exponentiality in categories of partial algebras.
Factorable congruences and strict refinement.
Finite atomistic lattices that can be represented as lattices of quasivarieties
We prove that a finite atomistic lattice can be represented as a lattice of quasivarieties if and only if it is isomorphic to the lattice of all subsemilattices of a finite semilattice. This settles a conjecture that appeared in the context of [11].
Finitely generated almost universal varieties of -lattices
A concrete category is (algebraically) universal if any category of algebras has a full embedding into , and is almost universal if there is a class of -objects such that all non-constant homomorphisms between them form a universal category. The main result of this paper fully characterizes the finitely generated varieties of -lattices which are almost universal.
Finitely generated congruence distributive quasivarieties of algebras