Congruence lattices of algebras in various varieties have been studied extensively in the literature. For example, congruence lattices (i.e. lattices of ideals) of Boolean algebras were characterized by Nachbin [18] (see also Gratzer [9] and Jonsson [16]) while congruence lattices of semilattices were investigated by Papert [19], Dean and Oehmke [4] and others. In this paper we initiate the inv...

Let S be a regular semigroup and let p be a congruence relation on S. The kernel of p, in notation kerp, is the union of the idempotent p-classes. The trace of p, in notation trp, is the restriction of p to the set of idempotents of S. The pair (kerp,trp) is said to be the congruence pair associated with p. Congruence pairs can be characterized abstractly, and it turns out that a congruence is ...

We derive a path counting formula for two-dimensional lattice model with filter restrictions in the presence of long steps, source and target points which are situated near filters. This solves problem finding an explicit multiplicities modules tensor product decomposition T(1)⊗N Uq(sl2) divided powers, where q is root unity. Combinatorial treatment this calls definition congruence regions mode...

The syntactic concept lattice is a residuated lattice associated with a given formal language; it arises naturally as a generalisation of the syntactic monoid in the analysis of the distributional structure of the language. In this paper we define the syntactic concept lattice and present its basic properties, and its relationship to the universal automaton and the syntactic congruence; we cons...

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We prove a general categorical theorem that enables us to state that under certain conditions, the range of a functor is large. As an application, we prove various results of which the following is a prototype: If every diagram, indexed by a lattice, of finite Boolean 〈∨, 0〉-semilattices with 〈∨, 0〉-embeddings, can be lifted with respect to the Conc functor on lattices, then so can every diagra...