The paper is devoted to inequalities between π0(X) and πd(X) where
π0(X) := min{π(U): U open and non-empty subset of X},
πd(X) := min{|????|: every open and dense subset of X containes an element from ????}.
From these definitions πd(X) ≤ π0(X) for every space X. In the paper we construct a space X for which πd(X)=ω1 and π0(X)=2ℵ0.
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Vol. 2 (1986)
Published: 1986-09-30
10.1515/amsil
English