Countably perfectly meager and countably perfectly null sets
Abstract
We study a strengthening of the notion of a universally meager set and its dual counterpart that strengthens the notion of a universally null set. We say that a subset of a perfect Polish space is countably perfectly meager (respectively, countably perfectly null) in , if for every perfect Polish topology on , giving the original Borel structure of , is covered by an -set in with the original Polish topology such that is meager with respect to (respectively, for every finite, non-atomic, Borel measure on , is covered by an -set in with ). We prove that if , then there exists a universally meager set in which is not countably perfectly meager in (respectively, a universally null set in which is not countably perfectly null in ).
Cite
@article{arxiv.2304.07579,
title = {Countably perfectly meager and countably perfectly null sets},
author = {Tomasz Weiss and Piotr Zakrzewski},
journal= {arXiv preprint arXiv:2304.07579},
year = {2023}
}