Combinatorics of open covers (VII): Groupability
Volume 179 / 2003
Fundamenta Mathematicae 179 (2003), 131-155
MSC: 54D20, 54C35, 54A25, 03E02, 91A44.
DOI: 10.4064/fm179-2-2
Abstract
We use Ramseyan partition relations to characterize:
the classical covering property of Hurewicz; \bullet the covering property of Gerlits and Nagy;\bullet the combinatorial cardinal numbers \mathfrak{b} and \mathsf{add}({\mathcal M}).
Let X be a \mathsf T_{3\frac{1}{2}}-space. In \cite{KS2} we showed that {\mathsf{C}}_{\rm p}(X) has countable strong fan tightness as well as the Reznichenko property if, and only if, all finite powers of X have the Gerlits–Nagy covering property. Now we show that the following are equivalent:1. {\mathsf{C}}_{\rm p}(X) has countable fan tightness and the Reznichenko property.
2. All finite powers of X have the Hurewicz property.
We show that for {\mathsf{C}}_{\rm p}(X) the combination of countable fan tightness with the Reznichenko property is characterized by a Ramseyan partition relation. Extending the work in \cite{KS2}, we give an analogous Ramseyan characterization for the combination of countable strong fan tightness with the Reznichenko property on {\mathsf{C}}_{\rm p}(X).
