English

A note on adding isomorphisms and the pseudointersection number

Logic 2025-10-14 v1 General Topology

Abstract

We prove that for every tower T\mathcal T there are 1\aleph_1-dense AA and BB so that any ``reasonable" forcing notion P\mathbb{P} -- an adjective that includes all known ones -- for making AA and BB isomorphic will add a pseudointersection for the tower. This shows in particular that MA1(σcentered)\mathsf{MA}_{\aleph_1}(\sigma{\rm -centered}) holds in all known models of BA\mathsf{BA}, which provides intrigue to well known questions of Todor\v{c}evi\'c and Stepr\=ans-Watson.

Keywords

Cite

@article{arxiv.2510.11155,
  title  = {A note on adding isomorphisms and the pseudointersection number},
  author = {Corey Bacal Switzer},
  journal= {arXiv preprint arXiv:2510.11155},
  year   = {2025}
}

Comments

11 pages, submitted

R2 v1 2026-07-01T06:33:27.257Z