Sh:1265

• Halbeisen, L. J., Horvath, S., & Shelah, S. A unique Q-point and infinitely many near-coherence classes of ultrafilters. Preprint. arXiv: 2505.17960
• Abstract:
  We show that in the model obtained by iteratively pseudo-intersecting a Ramsey ultrafilter via a length-\omega_2 countable support iteration of restricted Mathias forcing over a ground model satisfying \textsf{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^{\mathfrak{c}}-many near-coherence classes of ultrafilters.
• Version 2025-07-04 (11p)

@article{Sh:1265,
 author = {Halbeisen, Lorenz J. and Horvath, Silvan and Shelah, Saharon},
 title = {{A unique $Q$-point and infinitely many near-coherence classes of ultrafilters}},
 note = {\href{https://arxiv.org/abs/2505.17960}{arXiv: 2505.17960}},
 arxiv_number = {2505.17960}
}