The relation of rapid ultrafilters and Q-points to Van der Waerden ideal
More than a 0-point
We construct in ZFC an ultrafilter such that for every one-to-one function there exists with in the summable ideal, i.e. the sum of reciprocals of its elements converges. This strengthens Gryzlov’s result concerning the existence of -points.
A note on -ultrafilters and -points
Thin ultrafilters
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