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arXiv · 2605.09714

On skew ultralimits and their applications in ultrafilter theory

Nikolai L. Poliakov
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Abstract

We define a special version of the ultralimit, called the skewed ultralimit. Using this tool, we show that the set of ultrafilter types in the $C$-equivalence class of a Ramsey ultrafilter $\mathfrak u\in \beta\omega$ with the Rudin-Keisler order is isomorphic to the ultrapower of $(\omega, \leq)$.

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Nikolai L. Poliakov. 2026-05-10. On skew ultralimits and their applications in ultrafilter theory. https://arxiv.org/abs/2605.09714

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