English

Absolutely closed semigroups

General Topology 2023-01-09 v4 Group Theory

Abstract

Let C\mathcal C be a class of topological semigroups. A semigroup XX is called absolutelyabsolutely C\mathcal C-closedclosed if for any homomorphism h:XYh:X\to Y to a topological semigroup YCY\in\mathcal C, the image h[X]h[X] is closed in YY. Let T ⁣1S\mathsf{T_{\!1}S}, T ⁣2S\mathsf{T_{\!2}S}, and T ⁣zS\mathsf{T_{\!z}S} be the classes of T1T_1, Hausdorff, and Tychonoff zero-dimensional topological semigroups, respectively. We prove that a commutative semigroup XX is absolutely T ⁣zS\mathsf{T_{\!z}S}-closed if and only if XX is absolutely T ⁣2S\mathsf{T_{\!2}S}-closed if and only if XX is chain-finite, bounded, group-finite and Clifford+finite. On the other hand, a commutative semigroup XX is absolutely T ⁣1S\mathsf{T_{\!1}S}-closed if and only if XX is finite. Also, for a given absolutely C\mathcal C-closed semigroup XX we detect absolutely C\mathcal C-closed subsemigroups in the center of XX.

Keywords

Cite

@article{arxiv.2207.12778,
  title  = {Absolutely closed semigroups},
  author = {Taras Banakh and Serhii Bardyla},
  journal= {arXiv preprint arXiv:2207.12778},
  year   = {2023}
}

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22 pages