English

Semigroups uniquely determined by one-sided identity and zero sets

Group Theory 2026-05-26 v5

Abstract

For a groupoid SS with elements aa and bb, if ba=aba = a, then bb is a left identity of aa and aa is a right zero of bb. We define the left identity set of aa to be the set of all left identities of aa in SS, and similarly for the right identity set of aa in SS. We defined the left zero set of aa to be the set of all left zeroes of aa in SS, and similarly for the right zero set of aa. The one-sided identity and zero sets of a semigroup can be utilized in the determination of its maximal subgroups, maximal left and right zero subsemigroups, maximal left and right subgroups, and rectangular band subsemigroups. A band is an idempotent semigroup. Every commutative band is a semilattice and uniquely determined by the left and right identity sets of its elements or equivalently by the left and right zero sets of its elements. We generalize this notion by defining a groupoid or semigroup to be stabilized with respect to binary relations, in particular the binary relations defined by the one-sided identity and zero sets of its elements, if and only if for any groupoid or semigroup on the same set with the same binary relations, their binary operations are identical. We prove every right group with maximal subgroup size 22 is a stabilized semigroup with respect to the one-sided identity [zero] sets of its elements. We define a commutative-rectangular band to be a band in which every pair of elements either commutes or are generalized inverses of each other, and we prove a commutative-rectangular band is a stabilized semigroup with respect to the one-sided identity [zero] sets of its elements.

Keywords

Cite

@article{arxiv.2410.23473,
  title  = {Semigroups uniquely determined by one-sided identity and zero sets},
  author = {Julia Maddox},
  journal= {arXiv preprint arXiv:2410.23473},
  year   = {2026}
}
R2 v1 2026-06-28T19:42:08.270Z