Document Type
Article
Publication Date
1999
Abstract
We consider the following two selection principles for topological spaces:
[Principle 1:] { For each sequence of dense subsets, there is a sequence of points from the space, the n-th point coming from the n-th dense set, such that this set of points is dense in the space;
[Principle 2:]{ For each sequence of dense subsets, there is a sequence of finite sets, the n-th a subset of the n-th dense set, such that the union of these finite sets is dense in the space.
We show that for separable metric space X one of these principles holds for the space C_p(X) of realvalued continuous functions equipped with the pointwise convergence topology if, and only if, a corresponding principle holds for a special family of open covers of X. An example is given to show that these equivalences do not hold in general for Tychonoff spaces. It is further shown that these two principles give characterizations for two popular cardinal numbers, and that these two principles are intimately related to an infinite game that was studied by Berner and Juhasz.
Copyright Statement
This is the accepted, peer‐reviewed manuscript of an article whose final and definitive form has been published in Quaestiones Mathematicae 1999, 22: 109-130 © 1999 copyright NISC (Pty) Ltd. The Quaestiones Mathematicae is available online at: http://www.informaworld.com/.
Publication Information
Scheepers, Marion. (1999). "Combinatorics of Open Covers VI: Selectors for Sequences of Dense Sets". Quaestiones Mathematicae, 22(1999), 109-130. https://doi.org/10.1080/16073606.1999.9632063