C-closed functions
A topological space is said to be -Lindelöf [1] if every cover of by cozero sets of admits a countable subcover. In this paper, we obtain new characterizations and preservation theorems of -Lindelöf spaces.
Some results on cleavability theory are presented. We also show some new [16]'s results.
If is a space that can be mapped onto a metric space by a one-to-one mapping, then is said to have a weaker metric topology. In this paper, we give characterizations of sequence-covering compact images and sequentially-quotient compact images of spaces with a weaker metric topology. The main results are that (1) is a sequence-covering compact image of a space with a weaker metric topology if and only if has a sequence of point-finite -covers such that for each . (2) is a sequentially-quotient...