Factorable congruences and factorable congruence blocks on powers of a finite algebra
Factorable congruences and strict refinement.
Factor-union representation of phenotype systems.
Families of strongly projective graphs
We give several characterisations of strongly projective graphs which generalise in many respects odd cycles and complete graphs [7]. We prove that all known families of projective graphs contain only strongly projective graphs, including complete graphs, odd cycles, Kneser graphs and non-bipartite distance-transitive graphs of diameter d ≥ 3.
Fast algorithms for finding a subdirect decomposition and interesting congruences of finite algebras
Finite hull systems and their implication bases. (Endliche Hüllensysteme und ihre Implikationenbasen.)
Finitely generated relations and their applications to permutable and -permutable varieties
Formal Translation Monoid and Algebra Congruences in a Monodial Category.
Four-part semigroups - semigroups of Boolean operations
Four-part semigroups form a new class of semigroups which became important when sets of Boolean operations which are closed under the binary superposition operation f + g := f(g,...,g), were studied. In this paper we describe the lattice of all subsemigroups of an arbitrary four-part semigroup, determine regular and idempotent elements, regular and idempotent subsemigroups, homomorphic images, Green's relations, and prove a representation theorem for four-part semigroups.
Free groupoids with axioms of the form and/or .
Free trees and the optimal bound in Wehrung's theorem
We prove that there is a distributive (∨,0,1)-semilattice of size ℵ₂ such that there is no weakly distributive (∨,0)-homomorphism from to with 1 in its range, for any algebra A with either a congruence-compatible structure of a (∨,1)-semi-lattice or a congruence-compatible structure of a lattice. In particular, is not isomorphic to the (∨,0)-semilattice of compact congruences of any lattice. This improves Wehrung’s solution of Dilworth’s Congruence Lattice Problem, by giving the best cardinality...
Function minimum associated to a congruence on integral n-tuple space.
Fuzzy congruences on groups and rings.