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ON $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-UNFAVOURABLE SPACES

Published online by Cambridge University Press:  16 March 2020

HANFENG WANG*
Affiliation:
Department of Mathematics, Shandong Agricultural University, Taian 271018, China email [email protected]
WEI HE
Affiliation:
Institute of Mathematics, Nanjing Normal University, Nanjing 210046, China email [email protected]
JING ZHANG
Affiliation:
School of Mathematics and Statistics, Minnan Normal University, Zhangzhou 363000, China email [email protected]

Abstract

To study when a paratopological group becomes a topological group, Arhangel’skii et al. [‘Topological games and topologies on groups’, Math. Maced. 8 (2010), 1–19] introduced the class of $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-unfavourable spaces. We show that every $\unicode[STIX]{x1D707}$-complete (or normal) $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-unfavourable semitopological group is a topological group. We prove that the product of a $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-unfavourable space and a strongly Fréchet $(\unicode[STIX]{x1D6FC},G_{\unicode[STIX]{x1D6F1}})$-favourable space is $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-unfavourable. We also show that continuous closed irreducible mappings preserve the $(\,\unicode[STIX]{x1D6FD},G_{\unicode[STIX]{x1D6F1}})$-unfavourableness in both directions.

Type
Research Article
Copyright
© 2020 Australian Mathematical Publishing Association Inc.

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Footnotes

Project supported by SDNSF (No. ZR2018MA013) and NSFC (Nos. 11571175, 11801254).

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