Categories of partial algebras for critical points between varieties of algebras - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Algebra Universalis Année : 2014

Categories of partial algebras for critical points between varieties of algebras

Résumé

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.
Fichier principal
Vignette du fichier
gamps.pdf (510.21 Ko) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

hal-00544601 , version 1 (08-12-2010)

Identifiants

Citer

Pierre Gillibert. Categories of partial algebras for critical points between varieties of algebras. Algebra Universalis, 2014, 71, pp.299-357. ⟨10.1007/s00012-014-0279-y⟩. ⟨hal-00544601⟩
106 Consultations
62 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More