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Spaces with large relative extent
Authors:Yan-Kui Song
Institution:(1) Department of Mathematics, Nanjing Normal University, Nanjing, 210097, P.R. China
Abstract:In this paper, we prove the following statements: (1) For every regular uncountable cardinal κ, there exist a Tychonoff space X and Y a subspace of X such that Y is both relatively absolute star-Lindelöf and relative property (a) in X and e(Y, X) ? κ, but Y is not strongly relative star-Lindelöf in X and X is not star-Lindelöf. (2) There exist a Tychonoff space X and a subspace Y of X such that Y is strongly relative star-Lindelöf in X (hence, relative star-Lindelöf), but Y is not absolutely relative star-Lindelöf in X.
Keywords:relative topological property  Lindel?f  star-Lindel?f  relative extent  relative property (a)
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