Published online by Cambridge University Press: 17 April 2009
Completely simple semigroups form a variety if we consider them both with the multiplication and the operation of inversion. Denote the lattice of all varieties of completely simple semi-groups by L(CS) and that of varieties of groups by L(G). We prove that the mappings V → V ∩ G and V → V v G are homomorphisms of L(CS) onto L(G) and the interval [G, CS], respectively. The homomorphism V → (V ∩ G, V v G) is an isomorphism of L(CS) onto a subdirect product. We explore different properties of the congruences on L(CS) induced by these homomorphisms.
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