The maximum cardinality of essential families in regular or normal spaces

Rad Hrvatske akademije znanosti i umjetnosti Matematičke znanosti 2026 Open access

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Authors: Leonard R. Rubin
DOI: 10.21857/yl4okfkgv9
Cited by: 0

Abstract

Let X be a regular or normal space (T 1 not required) with infinite weight and C be an essential family in X.We will show that card C ≤ wt X.This implies that every essential family in a separable metrizable space is countable.

Fields of Study & Subjects

Advanced Topology and Set Theory Advanced Banach Space Theory Advanced Combinatorial Mathematics

Publication details

Journal / source
Rad Hrvatske akademije znanosti i umjetnosti Matematičke znanosti
Volume
30
Pages
169–176
Publication date
1 January 2026
Language
HR