2 citations · 6 across the 33 of their papers we have counts for
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Coordinatization of lattices by regular rings without unit and Banaschewski functions
Friedrich Wehrung
A Banaschewski function on a bounded lattice L is an antitone self-map of L that picks a complement for each element of L. We prove a set of results that include the following: (1)…
Embedding properties of endomorphism semigroups
Joao Araujo, Friedrich Wehrung
Denote by PSelf(X) (resp., Self(X)) the partial (resp., full) transformation monoid over a set X, and by Sub(V) (resp., End(V)) the collection of all subspaces (resp., endomorphism…
Embedding coproducts of partition lattices
Friedrich Wehrung
We prove that the lattice Eq(X) of all equivalence relations on an infinite set X contains, as a 0,1-sublattice, the 0-coproduct of two copies of itself, thus answering a question…
A solution to Dilworth's Congruence Lattice Problem
Friedrich Wehrung
We construct a distributive algebraic lattice D that is not isomorphic to the congruence lattice of any lattice. This solves a long-standing open problem, traditionally attributed…
Poset representations of distributive semilattices
Friedrich Wehrung
We prove that for any distributive join-semilattice S, there are a meet-semilattice P with zero and a map f:PxP-->S such that f(x,z)<=f(x,y)vf(y,z) and x<=y implies that f(x,y)=0,…
Congruence lifting of diagrams of finite Boolean semilattices requires large congruence varieties
Friedrich Wehrung, Jiri Tuma
We construct a diagram D, indexed by a finite partially ordered set, of finite Boolean semilattices and (v,0,1)-embeddings, with top semilattice , such that for any variety V…