Weak Baumgartner axioms and universal spaces
Abstract
If is a topological space and is a cardinal then is the statement that for each pair of -dense subsets there is an autohomeomorphism mapping to . In particular is equivalent the celebrated Baumgartner axiom on isomorphism types of -dense linear orders. In this paper we consider two natural weakenings of which we call and for arbitrary perfect Polish spaces . We show that the first of these, though properly weaker, entails many of the more striking consequences of while the second does not. Nevertheless the second is still independent of and we show in particular that it fails in the Cohen and random models. This motivates several new classes of pairs of spaces which are ``very far from being homeomorphic" which we call ``avoiding", ``strongly avoiding", and ``totally avoiding". The paper concludes by studying these classes, particularly in the context of forcing theory, in an attempt to gauge how different weak Baumgartner axioms may be separated.
Keywords
Cite
@article{arxiv.2502.10029,
title = {Weak Baumgartner axioms and universal spaces},
author = {Corey Bacal Switzer},
journal= {arXiv preprint arXiv:2502.10029},
year = {2025}
}
Comments
20 pages, submitted. Second version incorporates several recommendations from anonymous referees. In particular the terminology of "hating" etc has been changed