2009 seminar talk: A new upper bound on the cofinality of the infinite symmetric group
Talk held by Lyubomyr Zdomskyy (KGRC) at the KGRC seminar on 2009-04-02.
We shall prove that if an ultrafilter F is not coherent to a Q-point, then cof(sym(w)) ≤ b(F).
This improves some results of J. Sharp and S. Thomas.