Topological spaces compact with respect to a set of filters
Abstract
If is a family of filters over some set , a topological space is \emph{sequencewise -\brfrt compact} if, for every -indexed sequence of elements of , there is such that the sequence has an -limit point. Countable compactness, sequential compactness, initial -compactness, -compactness, the Menger and Rothberger properties can all be expressed in terms of sequencewise -compactness, for appropriate choices of . We show that sequencewise -compactness is preserved under taking products if and only if there is a filter such that sequencewise -compactness is equivalent to -compactness. If this is the case, and there exists a sequencewise -compact topological space with more than one point, then is necessarily an ultrafilter. The particular cases of sequential compactness and of -compactness are analyzed in detail.
Keywords
Cite
@article{arxiv.1210.2120,
title = {Topological spaces compact with respect to a set of filters},
author = {Paolo Lipparini},
journal= {arXiv preprint arXiv:1210.2120},
year = {2016}
}
Comments
v.2, some improvements, divided into sections