Abstract
After a brief survey of the theory of partition ordinals, i.e., ordinals α such that α → (α,n)2 for all n < ω, it is shown that MA(ℵ1) implies that ω1ω and ω1ω2 are partition ordinals. This contrasts with an old result of Erdős and Hajnal that α ↛ (α,3)2 holds for both these ordinals under the Continuum Hypothesis.
Preparation of this paper was partially supported by National Science Foundation grant number DMS-8704586.
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© 1989 Springer-Verlag
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Baumgartner, J.E. (1989). Remarks on partition ordinals. In: Steprāns, J., Watson, S. (eds) Set Theory and its Applications. Lecture Notes in Mathematics, vol 1401. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0097328
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DOI: https://doi.org/10.1007/BFb0097328
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