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Normality and dense subspaces
Authors:A. V. Arhangel'skii
Affiliation:Department of Mathematics, 321 Morton Hall, Ohio University, Athens, Ohio 45701
Abstract:

In the first section of this paper, using certain powerful results in $C_{p}$-theory, we show that there exists a nice linear topological space $X$of weight $omega _{1}$ such that no dense subspace of $X$ is normal. In the second and third sections a natural generalization of normality, called dense normality, is considered. In particular, it is shown in section 2 that the space $R^{c}$ is not normal on some countable dense subspace of it, while it is normal on some other dense subspace. An example of a Tychonoff space $X$, which is not densely normal on a dense separable metrizable subspace, is constructed. In section 3, a link between dense normality and relative countable compactness is established. In section 4 the result of section 1 is extended to densely normal spaces.

Keywords:Normal space, extent, Lindel"  {o}f number, Souslin number, $C_{p}$-theory, densely normal, $kappa $-normal, $X$ normal on $Y$, $A$ concentrated on $Y$, pseudocompact, relative countable compactness, locally connected
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