2010/12/09 by Pierre Gillibert, Gillibert, Pierre
Computer Science · Decision Sciences · Mathematics · #Advanced Algebra and Logic #Category Theory (math.CT) #FOS: Mathematics #Fuzzy and Soft Set Theory #Rough Sets and Fuzzy Logic #math.CT
paper · pdf · doi:10.48550/arxiv.1012.1949
47 pages
arxiv created 2010/12/09 · openalex publication_date 2010/12/09 · arxiv updated 2010/12/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A lifting of a semilattice S is an algebra A such that the semilattice of compact (=finitely generated) congruences of A is isomorphic to S. The aim of this work is to give a categorical theory of partial algebras endowed with a partial subalgebra together with a semilattice-valued distance, that we call gamps. This part of the theory is formulated in any variety of (universal) algebras. Let V and W be varieties of algebras (on a finite similarity type). Let P be a finite lattice of order-dimension d>0. Assume that we have a diagram of semilattice with a lifting in V, but with no "partial lifting" in the category of gamps of W, then there is a semilattice S of cardinality aleph (d - 1), such that S has a lifting in V, but S has no lifting in W. We already knew a similar result for diagrams with no lifting in W, however the semilattice S constructed here has cardinality aleph d. Gamps are also used to study congruence-preserving extensions. Denote by M the variety generated by the lattice of length two, with three atoms. We construct a lattice A in M of cardinality aleph 1 with no congruence n-permutable, congruence-preserving extension, for each n > 1.