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A polarized partition relation for cardinals of countable cofinality. (English) Zbl 1137.03028

For ordinals \(\alpha\), \(\beta\), \(\gamma_0\), \(\gamma_1\), \(\delta_0\), and \(\delta_1\), the balanced polarized partition relation
\[ \left(\begin{matrix} \alpha\\ \beta \end{matrix}\right) \rightarrow \left(\begin{matrix} \gamma_0 & \gamma_1\\ \delta_0 & \delta_1 \end{matrix}\right)^{1,1} \]
holds if for any partition of \(\beta\times\alpha=K_0\cup K_1\) into two classes, either there are \(D_0\in [\beta]^{\delta_0}\) and \(C_0\in [\alpha]^{\gamma_0}\) with \(D_0\times C_0\subseteq K_0\), or there are \(D_1\in [\beta]^{\delta_1}\) and \(C_1\in [\alpha]^{\gamma_1}\) with \(D_1\times C_1\subseteq K_1\). In the paper under review it is shown that if \(\text{cf}\kappa=\omega\) and \(\lambda=2^{<\kappa}\), then
\[ \left(\begin{matrix} \lambda^+\\ \lambda \end{matrix}\right) \rightarrow \left(\begin{matrix} \lambda^+ & \alpha\\ \lambda & \kappa \end{matrix}\right)^{1,1} \] for all \(\alpha<\omega_1\).

MSC:

03E05 Other combinatorial set theory
05D10 Ramsey theory
05A18 Partitions of sets
Full Text: DOI

References:

[1] J. Baumgartner and A. Hajnal, A proof (involving Martin’s axiom) of a partition relation, Fund. Math. 78 (1973), no. 3, 193 – 203. · Zbl 0257.02054
[2] G. V. Čudnovskiĭ, Combinatorial properties of compact cardinals, Infinite and finite sets (Colloq., Keszthely, 1973; dedicated to P. Erdős on his 60th birthday), Vol. I, North-Holland, Amsterdam, 1975, pp. 289 – 306. Colloq. Math. Soc. János Bolyai, Vol. 10.
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