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Algebra Universalis
Article . 1983 . Peer-reviewed
License: Springer TDM
Data sources: Crossref
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
zbMATH Open
Article . 1983
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A Mal'cev characterization of n-permutable varieties with directly decomposable congruences

Authors: Duda, Jaromir;

A Mal'cev characterization of n-permutable varieties with directly decomposable congruences

Abstract

A variety V has directly decomposable congruences (abbreviated: DDCon) if every congruence relation on the product A x B of algebras A, B s V is uniquely determined by its projections onto A and B. Varieties with DDCon are characterizable by Mal'cev condition, the concrete polynomial identities were derived by G. A. Fraser and A. Horn [2] and by T.-K. Hu [unpublished]. These identities are not simple and so the phenomenon of DDCon was investigated on varieties with some additional assumptions, e.g. the Mal'cev characterization of DDCon in a permutable variety with one idempotent nullary operation is well-known, see H. Werner [9]. Recently, using H. Werner's description of permutable varieties [8], I. Chajda [1] gave a Mal'cev characterization of DDCon in permutable varieties only. We show (in Corollary 1 of this paper) that the identities of [1] can be improved; our improvement is slight in form but essential since the Mal'cev polynomial p(x = p(x, y, y) = p(y, y, x)) can be derived from the new identities and thus they characterize permutability and direct decomposability of congruences in an arbitrary variety of algebras, i.e. the assumption of permutability is redundant now (compare [1] and Corollary 1 of this paper). Making use of J. Hagemann's and A. Mitschke's description of n-permutable varieties, see [4], we generalize the above mentioned result and so a Mal'cev characterization for n-permutable varieties with DDCon is obtained. In order not to have to interrupt the discussion later, recall firstly some

Keywords

Equational logic, Mal'tsev conditions, n-permutability, direct product of congruences, Subalgebras, congruence relations, implication algebras, Mal'cev condition, direct decomposability

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
1
Average
Average
Average
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