There may be no nowhere dense ultrafilter
Saharon Shelah
Abstract
We show the consistency of ZFC +''there is no NWD-ultrafilter on omega'', which means: for every non principle ultrafilter D on the set of natural numbers, there is a function f from the set of natural numbers to the reals, such that for some nowhere dense set A of reals, the set n: f(n) in A is not in D. This answers a question of van Douwen, which was put in more general context by Baumgartner
Create a lesson
Related papers
The universal measure of nonstochastic objects
Vladimir Vovk
Hyperarithmetic directions can all be exceptional for Marstrand's projection theorem
Noam Greenberg, Daniel Turetsky
Open Problems in Mathematical Logic
George Barmpalias, Su Gao, Jialiang He et al.
An easy proof that there may be no P-points
David Chodounský, Osvaldo Guzmán, Jonathan Verner
Comments on Choiceless Chain Conditions
Constance Bromham, Asaf Karagila
Localic Esakia Duality via Conic Frames
Nesta van der Schaaf