End extensions, conservative extensions, and the RudinFrolík ordering
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 by Andreas Blass PDF
 Trans. Amer. Math. Soc. 225 (1977), 325340 Request permission
Abstract:
The ordering of ultrafilters on the natural numbers defined by “Eprod N is an end extension of Dprod N,” the ordering defined by “Eprod N is a conservative extension of Dprod N,” and the RudinFrolik ordering are proved to be distinct if the continuum hypothesis holds. These three orderings are also characterized in terms of (not necessarily internal) ultrafilters in the Boolean algebra of internal sets of natural numbers in a nonstandard universe.References

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Additional Information
 © Copyright 1977 American Mathematical Society
 Journal: Trans. Amer. Math. Soc. 225 (1977), 325340
 MSC: Primary 02H13; Secondary 04A05
 DOI: https://doi.org/10.1090/S0002994719770424556X
 MathSciNet review: 0424556