Square-bracket operations clubs

Osvaldo Guzman; Stevo Todorcevic

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arXiv · 2602.14373

Square-bracket operations clubs

Osvaldo Guzman·Stevo Todorcevic

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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 $C\subseteq\omega_{1}$, there is an uncountable subset $W$ $\subseteq \omega_{1}$ such that $\left[ \alpha\beta\right] \in C$ for every $\alpha,\beta\in W.$ \ 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.

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BibTeX RIS

Osvaldo Guzman, Stevo Todorcevic. 2026-02-16. Square-bracket operations clubs. https://arxiv.org/abs/2602.14373

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