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Article

Simon, Petr
On the existence of true uniform ultrafilters. (English). Commentationes Mathematicae Universitatis Carolinae, vol. 45 (2004), issue 4, pp. 739-741
MSC: 54A20, 54D80, 54G05 | MR 2103088 | Zbl 1099.54006
Keywords:
uniform ultrafilter; linked family
Summary:
We shall show that there is an ultrafilter on singular $\kappa$ with countable cofinality, which cannot be reached from the set of all subuniform ultrafilters by iterating the closure of sets of size $<\kappa$.
References:
[CN] Comfort W.W., Negrepontis S.: The Theory of Ultrafilters. Springer, New York, Heidelberg, Berlin (1974). MR 0396267 | Zbl 0298.02004
[vD] van Douwen E.K.: Remote points. Dissertationes Math. 188 (1981), 1-45. MR 0627526 | Zbl 0525.54018
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