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Notes on strongly Whyburn spaces

Masami Sakai (2016)

Commentationes Mathematicae Universitatis Carolinae

We introduce the notion of a strongly Whyburn space, and show that a space X is strongly Whyburn if and only if X × ( ω + 1 ) is Whyburn. We also show that if X × Y is Whyburn for any Whyburn space Y , then X is discrete.

Nowhere dense subsets and Booth's Lemma

Viacheslav I. Malykhin (1996)

Commentationes Mathematicae Universitatis Carolinae

The following statement is proved to be independent from [ LB + ¬ CH ] : ( * ) Let X be a Tychonoff space with c ( X ) 0 and π w ( X ) < . Then a union of less than of nowhere dense subsets of X is a union of not greater than π w ( X ) of nowhere dense subsets.

Observations on spaces with zeroset or regular G δ -diagonals

Raushan Z. Buzyakova (2005)

Commentationes Mathematicae Universitatis Carolinae

We show that if X 2 has countable extent and X has a zeroset diagonal then X is submetrizable. We also make a couple of observations regarding spaces with a regular G δ -diagonal.

On character and chain conditions in images of products

Murray Bell (1998)

Fundamenta Mathematicae

A scadic space is a Hausdorff continuous image of a product of compact scattered spaces. We complete a theorem begun by G. Chertanov that will establish that for each scadic space X, χ(X) = w(X). A ξ-adic space is a Hausdorff continuous image of a product of compact ordinal spaces. We introduce an either-or chain condition called Property R λ ' which we show is satisfied by all ξ-adic spaces. Whereas Property R λ ' is productive, we show that a weaker (but more natural) Property R λ is not productive. Polyadic...

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