The union of two D-spaces need not be D
Dániel T. Soukup ; Paul J. Szeptycki
Fundamenta Mathematicae, Tome 220 (2013), p. 129-137 / Harvested from The Polish Digital Mathematics Library
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We construct from ⋄ a T₂ example of a hereditarily Lindelöf space X that is not a D-space but is the union of two subspaces both of which are D-spaces. This answers a question of Arhangel'skii.

Publié le : 2013-01-01
EUDML-ID : urn:eudml:doc:282738 
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Dániel T. Soukup; Paul J. Szeptycki. The union of two D-spaces need not be D. Fundamenta Mathematicae, Tome 220 (2013) pp. 129-137. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-fm220-2-3/