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Article
Combinatorial Rees–Sushkevich Varieties That Are Cross, Finitely Generated, Or Small
Bulletin of the Australian Mathematical Society
  • Edmond W. H. Lee, Nova Southeastern University
Document Type
Article
Publication Date
2-1-2010
Keywords
  • Primary 20M07,
  • Secondary 03C05,
  • 08B15
Disciplines
Abstract

A variety is said to be a Rees–Sushkevich variety if it is contained in a periodic variety generated by 0-simple semigroups. Recently, all combinatorial Rees–Sushkevich varieties have been shown to be finitely based. The present paper continues the investigation of these varieties by describing those that are Cross, finitely generated, or small. It is shown that within the lattice of combinatorial Rees–Sushkevich varieties, the set ℱ of finitely generated varieties constitutes an incomplete sublattice and the set � of small varieties constitutes a strict incomplete sublattice of ℱ. Consequently, a combinatorial Rees–Sushkevich variety is small if and only if it is Cross. An algorithm is also presented that decides if an arbitrarily given finite set Σ of identities defines, within the largest combinatorial Rees–Sushkevich variety, a subvariety that is finitely generated or small. This algorithm has complexity �(nk) where n is the number of identities in Σ and k is the length of the longest word in Σ.

ORCID ID
0000-0002-1662-3734
ResearcherID
I-6970-2013
DOI
10.1017/S0004972709000616
Citation Information
Edmond W. H. Lee. "Combinatorial Rees–Sushkevich Varieties That Are Cross, Finitely Generated, Or Small" Bulletin of the Australian Mathematical Society Vol. 81 Iss. 1 (2010) p. 64 - 84 ISSN: 0004-9727
Available at: http://works.bepress.com/edmond-lee/29/