PFA and the definability of the nonstationary ideal
Abstract
We produce, relative to a ZFC model with a supercompact cardinal, a ZFC model of the Proper Forcing Axiom in which the nonstationary ideal on ω1 is 1-definable in a parameter from H_2.
0
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.