A unique Q-point and infinitely many near-coherence classes of ultrafilters
We show that in the model obtained by iteratively pseudo-intersecting a Ramsey ultrafilter via a length-ω2 countable support iteration of restricted Mathias forcing over a ground model satisfying CH, there is a unique Q-point up to isomorphism. In particular, it is consistent that there is only one Q-point while there are 2<sup>c</sup>-many near-coherence classes of ultrafilters.
Authors
- Lorenz Halbeısen (ORCID: https://orcid.org/0000-0001-6078-7237)
- Silvan Horvath
- Saharon Shelah
Publication Details
- Journal
- Annals of Pure and Applied Logic
- Published
- 2026-03-02
- DOI
- https://doi.org/10.1016/j.apal.2026.103747
- Primary Topic
- Holomorphic and Operator Theory
- Type
- article
- Field-Weighted Citation Impact
- 0.00