A generalization of the direct product of universal algebras
A groupoid characterization of Boolean algebras
We present a groupoid which can be converted into a Boolean algebra with respect to term operations. Also conversely, every Boolean algebra can be reached in this way.
A lattice of homomorphs
A matrix characterization of the maximal groups in
A multiplication of -varieties of orthodox semigroups
We define semantically a partial multiplication on the lattice of all e–varieties of regular semigroups. In the case that the first factor is an e–variety of orthodox semigroups we describe our multiplication syntactically in terms of biinvariant congruences.
A multiplication of e-varieties of regular -solid semigroups by inverse semigroup varieties
A multiplication of e-varieties of regular -solid semigroups by inverse semigroup varieties is described both semantically and syntactically. The associativity of the multiplication is also proved.
A new example of a limit variety.
A new Proof of Prešić's Theorem on Finite Equations
A new proof of Reiterman's theorem
A New Proof of the Eilenberg-Zilber-Cartier Theorem.
A non-commutative free algebra of rank 0
A normal form for restricted exponential functions
A note on algebraic categories
A note on categories of partial algebras
A note on coclones of topological spaces
The clone of a topological space is known to have a strictly more expressive first-order language than that of the monoid of continuous self-maps. The current paper studies coclones of topological spaces (i.e. clones in the category dual to that of topological spaces and continuous maps) and proves that, in contrast to clones, the first-order properties of coclones cannot express anything more than those of the monoid, except for the case of discrete and indiscrete spaces.
A note on cylindric lattices
0. Introduction. Besides being of intrinsic interest, cylindric (semi-) lattices arise naturally from the study of dependencies in relational databases; the polynomials on a cylindric semilattice are closely related to the queries obtainable from project-join mappings on a relational database (cf. [D] for references). This note is intended to initiate the study of these structures, and only a few, rather basic results will be given. Some problems at the end will hopefully stimulate further research....
A note on dual discriminator varieties.
A note on finite sets of terms closed under subterms and unification
The paper contains two remarks on finite sets of groupoid terms closed under subterms and the application of unifying pairs.
A note on functionally complete algebras
A Note on Functionally Complete Algebras with no Non-Trivial Subalgebras.