On semigroups which admit only discrete left-continuous Hausdorff topology

Fuente: arXiv
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Autore principale: Gutik, Oleg
Natura: Preprint
Pubblicazione: 2026
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author Gutik, Oleg
author_facet Gutik, Oleg
contents We give the sufficient condition when every left-continuous (right-continuous) Hausdorff topology on a semigroup $S$ is discrete. We construct a submonoid $\mathscr{C}_{+}(a,b)$ (resp., $\mathscr{C}_{-}(a,b)$) of the bicyclic monoid which contains a family $\{S_α\colon α\in\mathfrak{c}\}$ of continuum many subsemigroups with the following properties: $(i)$ every left-continuous (resp., right-continuous) Hausdorff topology on $S_α$ is discrete; $(ii)$ every semigroup $S_α$ admits a non-discrete right-continuous (resp., left-continuous) Hausdorff topology which is not left-continuous (resp., right-continuous); $(iii)$ every semigroup $S_α$ isomorphically embeds into a Hausdorff compact topological semigroup. Also we construct a submonoid $\mathscr{C}_{\mathbb{Z}}^+$ (resp., $\mathscr{C}_{\mathbb{Z}}^-$) of the extended bicyclic semigroup which contains a family $\{S_α\colon α\in\mathfrak{c}\}$ of continuum many subsemigroups with the above described properties.
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publishDate 2026
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spellingShingle On semigroups which admit only discrete left-continuous Hausdorff topology
Gutik, Oleg
Group Theory
General Topology
22A15, 54C08, 54D10, 54D30, 54E52, 54H10
We give the sufficient condition when every left-continuous (right-continuous) Hausdorff topology on a semigroup $S$ is discrete. We construct a submonoid $\mathscr{C}_{+}(a,b)$ (resp., $\mathscr{C}_{-}(a,b)$) of the bicyclic monoid which contains a family $\{S_α\colon α\in\mathfrak{c}\}$ of continuum many subsemigroups with the following properties: $(i)$ every left-continuous (resp., right-continuous) Hausdorff topology on $S_α$ is discrete; $(ii)$ every semigroup $S_α$ admits a non-discrete right-continuous (resp., left-continuous) Hausdorff topology which is not left-continuous (resp., right-continuous); $(iii)$ every semigroup $S_α$ isomorphically embeds into a Hausdorff compact topological semigroup. Also we construct a submonoid $\mathscr{C}_{\mathbb{Z}}^+$ (resp., $\mathscr{C}_{\mathbb{Z}}^-$) of the extended bicyclic semigroup which contains a family $\{S_α\colon α\in\mathfrak{c}\}$ of continuum many subsemigroups with the above described properties.
title On semigroups which admit only discrete left-continuous Hausdorff topology
topic Group Theory
General Topology
22A15, 54C08, 54D10, 54D30, 54E52, 54H10
url https://arxiv.org/abs/2601.19881