Left quasi-abundant semigroups
J. Korean Math. Soc. 2019 Vol. 56, No. 5, 1159-1172
Published online September 1, 2019
Zhulin Ji, Xueming Ren, Yanhui Wang
Xi'an University of Architecture and Technology; Xi'an University of Architecture and Technology; Shandong University of Science and Technology
Abstract : A semigroup $S$ is called a weakly abundant semigroup if its every $\widetilde{\mathcal{L}}$-class and every $\widetilde{\mathcal{R}}$-class contains an idempotent. Our purpose is to study an analogue of orthodox semigroups in the class of weakly abundant semigroups. Such an analogue is called a left quasi-abundant semigroup, which is a weakly abundant semigroup with a left quasi-normal band of idempotents and having the congruence condition (C). To build our main structure theorem for left quasi-abundant semigroups, we first give a sufficient and necessary condition of the idempotent set $E(S)$ of a weakly abundant semigroup $S$ being a left quasi-normal band. And then we construct a left quasi-abundant semigroup in terms of weak spined products. Such a result is a generalisation of that of Guo and Shum for left semi-perfect abundant semigroups. In addition, we consider a type $Q$ semigroup which is a left quasi-abundant semigroup having the PC condition.
Keywords : weakly abundant semigroups, weak spined products, left quasi-abundant semigroups, type $Q$ semigroups
MSC numbers : 20M10
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