L. Halbeisen

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math.LO2026

A unique $Q$ -point and infinitely many near-coherence classes of ultrafilters

Lorenz Halbeisen, Silvan Horvath, Saharon Shelah

We show that in the model obtained by iteratively pseudo-intersecting a Ramsey ultrafilter via a length- $I ¨ _{2}$ countable support iteration of restricted Mathias forcing over a grou…

math.LO2025

There may be exactly $n$ $Q$ -points

Lorenz Halbeisen, Silvan Horvath, Tan Ãzalp

We generalize the main result of arXiv:2505.17960 and show the consistency of the statement ``There are exactly $n$ $Q$ -points up to isomorphism" for any finite $n$ . Furthermore, w…

A unique Q-point and infinitely many near-coherence classes of ultrafilters

There may be exactly n Q-points

A unique $Q$ -point and infinitely many near-coherence classes of ultrafilters

There may be exactly $n$ $Q$ -points