Article
Keywords:
principal left ideal; direct product; direct product of two semigroups
Summary:
A necessary and sufficient condition is given for a) a principal left ideal $L(s,t)$ in $S\times T$ to be equal to the direct product of the corresponding principal left ideals $L(s)\times L(t)$, b) an $\Cal L$-class $L_{(s,t)}$ to be equal to the direct product of the corresponding $\Cal L$-classes $L_s\times L_t$.
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