Regular rigid Korovin orbits

Abstract An example of an infinite regular feebly compact quasitopological group is presented such that all continuous real-valued functions on the group are constant. The example delineates the boundaries for possible generalizations of Banakh–Ravsky’s theorem concerning the complete regularity of regular paratopological groups. Our construction is based on the use of Korovin orbits in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> , where X is a special regular countably compact space constructed by Bardyla and Zdomskyy and G is an abstract Abelian group of an appropriate cardinality. Also, we study the interplay between the separation properties of the space X and Korovin orbits in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> . We show in particular that if X contains two nonempty disjoint open subsets, then every Korovin orbit in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> is Hausdorff. Several open problems in the field are presented.

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Journal
Revista de la Real Academia de Ciencias Exactas Físicas y Naturales Serie A Matemáticas
Published
2025-10-16
DOI
https://doi.org/10.1007/s13398-025-01797-y
Primary Topic
Geometric and Algebraic Topology
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article
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article

Regular rigid Korovin orbits

Mikhail Tkachenko, Evgenii Reznichenko
Revista de la Real Academia de Ciencias Exactas Físicas y Naturales Serie A Matemáticas
Geometric and Algebraic Topology
article

Regular rigid Korovin orbits

Mikhail Tkachenko, Evgenii Reznichenko
article en

Abstract

Abstract An example of an infinite regular feebly compact quasitopological group is presented such that all continuous real-valued functions on the group are constant. The example delineates the boundaries for possible generalizations of Banakh–Ravsky’s theorem concerning the complete regularity of regular paratopological groups. Our construction is based on the use of Korovin orbits in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> , where X is a special regular countably compact space constructed by Bardyla and Zdomskyy and G is an abstract Abelian group of an appropriate cardinality. Also, we study the interplay between the separation properties of the space X and Korovin orbits in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> . We show in particular that if X contains two nonempty disjoint open subsets, then every Korovin orbit in $$X^G$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>X</mml:mi> <mml:mi>G</mml:mi> </mml:msup> </mml:math> is Hausdorff. Several open problems in the field are presented.

Revista de la Real Academia de Ciencias Exactas Físicas y Naturales Serie A MatemáticasVol. 120(1)
Lomonosov Moscow State University (RU), Universidad Autónoma Metropolitana (MX)
Openalex Percentile: Top 65%
Geometric and Algebraic Topology
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Regular rigid Korovin orbits — Mikhail Tkachenko, Evgenii Reznichenko · Revista de la Real Academia de Ciencias Exactas Físicas y Naturales Serie A Matemáticas (2025) | TGRS Research Map | TGRS