One More Categorical Model of Universal Algebra.
One-element extensions in the variety generated by tournaments
We investigate congruences in one-element extensions of algebras in the variety generated by tournaments.
Operators and products in the lattice of existence varieties of regular semigroups.
Orthocomplemented difference lattices with few generators
The algebraic theory of quantum logics overlaps in places with certain areas of cybernetics, notably with the field of artificial intelligence (see, e. g., [19, 20]). Recently an effort has been exercised to advance with logics that possess a symmetric difference ([13, 14]) - with so called orthocomplemented difference lattices (ODLs). This paper further contributes to this effort. In [13] the author constructs an ODL that is not set-representable. This example is quite elaborate. A main result...
Orthorings
Certain ring-like structures, so-called orthorings, are introduced which are in a natural one-to-one correspondence with lattices with 0 every principal ideal of which is an ortholattice. This correspondence generalizes the well-known bijection between Boolean rings and Boolean algebras. It turns out that orthorings have nice congruence and ideal properties.
-compatible identities and their applications to classical algebras
Permutability, Distributivity of Equivalence Relations and Direct Products
Permutability of congruences in varieties with idempotent operations
Permutability of distributive congruence relations in a joint semilattice directed below
Permutability of tolerances with factor and decomposing congruences.
Polynome und algebraische Gleichungen über universalen Algebren.
Polynomial Interpolation and the Chinese Remainder Theorem for Algebraic Systems.
Polynomial Interpolation for Locally Equational Classes.
Polynomials in idempotent commutative groupoids [Book]
Poproduct of Lattices and Sorkin's Theorem
Positively conditional pseudovarieties and implicit operations on them.
Präprimale Algebren, die arithmetische Varietäten erzeugen
Precomplete varieties of semigroups.
Preservation Theorems for Limits of Structures and Global Sections of Sheaves of Structures.
Presolid varieties of n-semigroups
he class of all M-solid varieties of a given type t forms a complete sublattice of the lattice ℒ(τ) of all varieties of algebrasof type t. This gives a tool for a better description of the lattice ℒ(τ) by characterization of complete sublattices. In particular, this was done for varieties of semigroups by L. Polák ([10]) as well as by Denecke and Koppitz ([4], [5]). Denecke and Hounnon characterized M-solid varieties of semirings ([3]) and M-solid varieties of groups were characterized by Koppitz...