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Proceedings of the American Mathematical Society

Published by the American Mathematical Society since 1950, Proceedings of the American Mathematical Society is devoted to shorter research articles in all areas of pure and applied mathematics.

ISSN 1088-6826 (online) ISSN 0002-9939 (print)

The 2020 MCQ for Proceedings of the American Mathematical Society is 0.85.

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A regular Lindelöf semimetric space which has no countable network


Author: E. S. Berney
Journal: Proc. Amer. Math. Soc. 26 (1970), 361-364
MSC: Primary 54.40
DOI: https://doi.org/10.1090/S0002-9939-1970-0270336-7
MathSciNet review: 0270336
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Abstract: A completely regular semimetric space $M$ is constructed which has no $\sigma$-discrete network. The space $M$ constructed has the property that every subset of $M$ of cardinality ${2^{{\aleph _0}}}$ contains a limit point of itself; thus, assuming ${2^{{\aleph _0}}} = {\aleph _1},M$ is Lindelöf. It is also shown from the same space $M$ that, assuming ${2^{{\aleph _0}}} = {\aleph _1}$, there exists a regular Lindelöf semimetric space $X$ such that $X \times X$ is not normal (hence not Lindelöf).


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Keywords: <IMG WIDTH="18" HEIGHT="20" ALIGN="BOTTOM" BORDER="0" SRC="images/img1.gif" ALT="$\sigma$">-discrete, network, symmetric space, semimetric space
Article copyright: © Copyright 1970 American Mathematical Society