English

Distinguishing Internally Club and Approachable on an Infinite Interval

Logic 2024-04-24 v1

Abstract

Krueger showed that PFA implies that for all regular Θ2\Theta \ge \aleph_2, there are stationarily many [H(Θ)]1[H(\Theta)]^{\aleph_1} that are internally club but not internally approachable. From countably many Mahlo cardinals, we force a model in which, for all positive n<ωn<\omega and Θn+1\Theta \ge \aleph_{n+1}, there is a stationary subset of [H(Θ)]n[H(\Theta)]^{\aleph_n} consisting of sets that are internally club but not internally approachable. The theorem is obtained using a new variant of Mitchell forcing. This answers questions of Krueger.

Keywords

Cite

@article{arxiv.2404.15230,
  title  = {Distinguishing Internally Club and Approachable on an Infinite Interval},
  author = {Hannes Jakob and Maxwell Levine},
  journal= {arXiv preprint arXiv:2404.15230},
  year   = {2024}
}