Abstract
Let I, H, S, P be the usual class operators on universal algebras. For a class K of universal algebras of the same type, let R({K}) be the class of all algebras isomorphic to a retract of a member of K and let R denote the corresponding class operator. In this paper the semigroup generated by class operators I, R, H, S, P and the corresponding partially ordered set are described. Also the standard semigroups of the above operators are determined for some varieties.
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Madarász, R.S., Tasić, B. On the Partially Ordered Semigroup Generated by the Class Operators I,R,H,S,P. Order 18, 49–60 (2001). https://doi.org/10.1023/A:1010614400132
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DOI: https://doi.org/10.1023/A:1010614400132