One Repeat Point Gives a Closed, Unbounded Ultrafilter on {ω_1}
arXiv:1403.4690
Abstract
It is shown that the consistency strength of ZF + DC + "the closed unbounded ultrafilter on omega_1 is an ultrafilter" is exactly ZFC + one measurable cardinal.
The proof is incorrect, and I doubt that the construction will in fact produce the desired ultrafilter