On the Weight of Nowhere Dense Subsets in Compact Spaces |
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Authors: | Ivanov A V |
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Abstract: | We study a new cardinal-valued invariant ndw(X) (calling it the nd-weight of X) of a topological space which is defined as the least upper bound of the weights of nowhere dense subsets of X. The main result is the proof of the inequality hl(X)ndw(X) for compact sets without isolated points ((hl is the hereditary Lindelof number). This inequality implies that a compact space without isolated points of countable nd-weight is completely normal. Assuming the continuum hypothesis, we construct an example of a nonmetrizable compact space of countable nd-weight without isolated points. |
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Keywords: | compact space nowhere dense set hereditary Lindelof number nd-weight |
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