Increasing chains and discrete reflection of cardinality
- Autori: SPADARO, SANTI DOMENICO
- Anno di pubblicazione: 2013
- Tipologia: Articolo in rivista
- OA Link: http://hdl.handle.net/10447/480948
Abstract
Combining ideas from two of our previous papers, we refine Arhangel'skii Theorem by proving a cardinal inequality of which this is a special case: any increasing union of strongly discretely Lindelof spaces with countable free sequences and countable pseudocharacter has cardinality at most continuum. We then give a partial positive answer to a problem of Alan Dow on reflection of cardinality by closures of discrete sets.