English

Square-bracket operations clubs

Logic 2026-02-17 v1

Abstract

This paper continues the investigation of the three square-bracket operations [][\cdot\cdot] from chapter 5 of \cite{Walks}. \ We say that a square-bracket operation [][\cdot\cdot] has the \emph{Ramsey club property} if for every club Cω1C\subseteq\omega_{1}, there is an uncountable subset WW ω1\subseteq \omega_{1} such that [αβ]C\left[ \alpha\beta\right] \in C for every α,βW.\alpha,\beta\in W. \ The second author proved that the Proper Forcing Axiom\textsf{ }implies that all the square-bracket operations induced by Aronszajn trees have this property. We extend this result to the other two classes. We conclude that each of the statements \textquotedblleft all square-bracket operations have the Ramsey club property\textquotedblright\ and \textquotedblleft No square-bracket operation has the Ramsey club property\textquotedblright\ are consistent with \textsf{ZFC. }In other words, \textsf{ZFC }is unable to decide the status of the Ramsey club property for any square-bracket operation. Furthermore, we analyze the status of the Ramsey club property for square-bracket operations under Martin's Axiom and the Continuum Hypothesis.

Cite

@article{arxiv.2602.14373,
  title  = {Square-bracket operations clubs},
  author = {Osvaldo Guzman and Stevo Todorcevic},
  journal= {arXiv preprint arXiv:2602.14373},
  year   = {2026}
}
R2 v1 2026-07-01T10:37:52.635Z