1Department of Mathematics University of Toronto Toronto, ON, M5S 1A1 Canada 2Department of Mathematics and Statistics York University Toronto, ON, M3J 1P3 Canada
Fundamenta Mathematicae, Tome 220 (2013) no. 2, pp. 129-137
We construct from $\diamondsuit $ a $T_2$ 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.
Keywords:
construct diamondsuit example hereditarily lindel space d space union subspaces which d spaces answers question arhangelskii
Affiliations des auteurs :
Dániel T. Soukup
1
;
Paul J. Szeptycki
2
1
Department of Mathematics University of Toronto Toronto, ON, M5S 1A1 Canada
2
Department of Mathematics and Statistics York University Toronto, ON, M3J 1P3 Canada
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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) no. 2, pp. 129-137. doi: 10.4064/fm220-2-3
