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Characters of ultrafilters and tightness of products of fans
Authors:Miroslav Hušek
Institution:a Charles University, Sokolovská 83, 18675 Prague, Czech Republic
b Univerzita J.E.Purkyně, ?eské mláde?e 8, 400 96 Ústí nad Labem, Czech Republic
Abstract:As applications of productivity of coreflective classes of topological spaces, the following results will be proved: (1) Characters of points of βN?N are not smaller than any submeasurable cardinal less or equal to ω2. (2) If κ is a submeasurable cardinal and S is a sequential fan with κ many spines then the tightness of the κ-power of S is equal to κ. In fact, a little more general results are proved.
Keywords:54A25  03E10
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