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Some points in βN

Published online by Cambridge University Press:  24 October 2008

Kenneth Kunen
Affiliation:
University of Wisconsin

Abstract

Assuming either the continuum hypothesis or Martin's axiom, we show that in the space βNN, there are: (a) points which are not P-points, but which are also not limit points of any countable set, and (b) a countable set of points dense in itself such that each of the points is not a limit point of any countable discrete set. Our method is to construct such points in the Stone space of a measure algebra, and then embed that Stone space into βNN. We also, by a similar use of measures, establish the independence of the existence of selective ultrafilters by showing that there are none in the random real model.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1976

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