
doi: 10.1007/bf02574350
An element \(a\) of a semigroup \((S,.)\) is called left (right) magnifying if there exists a proper subset \(M\) of \(S\) such that \(aM=S\) (\(Ma=S\)). \textit{K. Tolo} [Pac. J. Math. 31, 523--535 (1969; Zbl 0188.05401)] investigated the relationship between the existence of particular such elements in a semigroup \(S\) and the property of \(S\) to be factorizable, i.e. \(S=A.B\) for some proper subsemigroups \(A\), \(B\) of \(S\). Magnifying elements in semigroups with one-sided identity were also studied by \textit{V. Shvarc} and \textit{I. Jaroker} [Usp. Mat. Nauk 19, No. 4(118), 209--214 (1964; Zbl 0241.20053)]. In the paper under review the authors continue the investigation of such elements in simple and bisimple semigroups, respectively. In particular, it is shown that left magnifying elements exist 1) in a simple semigroup \(S\) with left identity iff \(S\) is not a right group, 2) in a bisimple semigroup \(S\) iff \(S\) is not a right group and contains a left identity or \(S\) is right simple and contains no idempotents, 3) in a regular semigroup \(S\) iff \(S\) admits a left identity \(e\) and an element \(t\in S\) such that \(tS=S\), \(te=t\) and \(e\notin St\). Finally, it is proved that every left (right) magnifying element of a semigroup \(S\) is maximal in the natural partial order of \(S\) [see the reviewer, Proc. Am. Math. Soc. 97, 384--388 (1986; Zbl 0596.06015)].
510.mathematics, bisimple semigroups, left magnifying elements, natural partial order, General structure theory for semigroups, simple semigroup, Article, regular semigroup
510.mathematics, bisimple semigroups, left magnifying elements, natural partial order, General structure theory for semigroups, simple semigroup, Article, regular semigroup
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