A partically ordered space which is not a Priestely space.
A Priestley view of spatialization of frames
A principal congruence identity characterizing the variety of distributive lattices with zero
A problem of A. Monteiro concerning relative complementation of lattices
A reduction theorem for ring varieties whose subvariety lattice is distributive
We prove a theorem (for arbitrary ring varieties and, in a stronger form, for varieties of associative rings) which basically reduces the problem of a description of varieties with distributive subvariety lattice to the case of algebras over a finite prime field.
A representation of relatively complemented distributive lattices
A representation theorem for tense -valued Łukasiewicz-Moisil algebras
In 2000, Figallo and Sanza introduced -valued Łukasiewicz-Moisil algebras which are both particular cases of matrix Łukasiewicz algebras and a generalization of -valued Łukasiewicz-Moisil algebras. Here we initiate an investigation into the class tLM of tense -valued Łukasiewicz-Moisil algebras (or tense LM-algebras), namely -valued Łukasiewicz-Moisil algebras endowed with two unary operations called tense operators. These algebras constitute a generalization of tense Łukasiewicz-Moisil algebras...
A scheme for congruence semidistributivity
A diagrammatic statement is developed for the generalized semidistributive law in case of single algebras assuming that their congruences are permutable. Without permutable congruences, a diagrammatic statement is developed for the ∧-semidistributive law.
A short note on lattices allowing disjunctive reasoning.
This short note shows that the scheme of disjunctive reasoning, a or b, not b : a, does not hold neither in proper ortholattices nor in proper de Morgan algebras. In both cases the scheme, once translated into the inequality b' · (a+b) ≤ a, forces the structure to be a boolean algebra.
A short note on separable frames
Following the introduction of separability in frames ([2]) we investigate further properties of this notion and establish some consequences of the Urysohn metrization theorem for frames that are frame counterparts of corresponding results in spaces. In particular we also show that regular subframes of compact metrizable frames are metrizable.
A subdirectly irreducible symmetric Heyting algebra which is not simple.
A sufficient condition of full normality
We present a direct constructive proof of full normality for a class of spaces (locales) that includes, among others, all metrizable ones.
A survey of hereditary properties of graphs
In this paper we survey results and open problems on the structure of additive and hereditary properties of graphs. The important role of vertex partition problems, in particular the existence of uniquely partitionable graphs and reducible properties of graphs in this structure is emphasized. Many related topics, including questions on the complexity of related problems, are investigated.
A ternary variety generated by lattices
A topological duality for the -chains associated with the logic
In this paper we present a topological duality for a certain subclass of the -structures defined by M. M. Fidel, which conform to a non-standard semantics for the paraconsistent N. C. A. da Costa logic . Actually, the duality introduced here is focused on -structures whose supports are chains. For our purposes, we characterize every -chain by means of a new structure that we will call down-covered chain (DCC) here. This characterization will allow us to prove the dual equivalence between the...
Abgeschlossene vollständige -Untergruppen der Verbandsgruppen
About Generalized Ideals in a Distributive Lattice.
Additive closure operators on abelian unital -groups
In the paper an additive closure operator on an abelian unital -group is introduced and one studies the mutual relation of such operators and of additive closure ones on the -algebra .
Affine complete algebras abstracting Kleene and Stone algebras.
Affine complete algebras generalizing Kleene and Stone algebras.