A class ℱ of universal algebras is called a formation if the following conditions are satisfied: 1) Any homomorphic image of A ∈ ℱ is in ℱ; 2) If α₁, α₂ are congruences on A and , i = 1,2, then A/(α₁∩α₂) ∈ ℱ. We prove that any formation generated by a simple algebra with permutable congruences is minimal, and hence any formation containing a simple algebra, with permutable congruences, contains a minimum subformation. This result gives a partial answer to an open problem of Shemetkov and Skiba on formations of finite universal algebras proposed in 1989.
@article{bwmeta1.element.bwnjournal-article-doi-10_7151_dmgaa_1037, author = {Wenbin Guo and K.P. Shum}, title = {Minimal formations of universal algebras}, journal = {Discussiones Mathematicae - General Algebra and Applications}, volume = {21}, year = {2001}, pages = {201-205}, zbl = {1059.08007}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_7151_dmgaa_1037} }
Wenbin Guo; K.P. Shum. Minimal formations of universal algebras. Discussiones Mathematicae - General Algebra and Applications, Tome 21 (2001) pp. 201-205. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_7151_dmgaa_1037/
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