English

Aronszajn Free Kurepa Trees

Logic 2023-10-20 v3

Abstract

We consider a transitive relation on the power set of ω1\omega_1 and show if there is a maximal element with respect to this relation then there is a Kurepa tree with no Aronszajn subtree. We also show that if there is a maximal subset of ω1\omega_1, then there are Kurepa trees which are not club isomorphic. These maximal subsets of ω1\omega_1 exist in many known models that are obtained from the constructible universe without large cardinal assumptions. For instance, whenever α0ω1\alpha_0 \in \omega_1 and Xω1X \subset \omega_1 are such that ω1\textscL[Xα0]=ω1,ω2\textscL[X]=ω2\omega_1^{\textsc{L}[X \cap \alpha_0]} = \omega_1, \omega_2^{\textsc{L}[X]} = \omega_2 and \textscV\textsc{V} is a semiproper forcing extension of \textscL[X]\textsc{L}[X] then XX is maximal in \textscV\textsc{V}.

Keywords

Cite

@article{arxiv.2010.06814,
  title  = {Aronszajn Free Kurepa Trees},
  author = {Hossein Lamei Ramandi and Stevo Todorcevic},
  journal= {arXiv preprint arXiv:2010.06814},
  year   = {2023}
}
R2 v1 2026-06-23T19:19:49.953Z