Graph explorer

Strong Projective Witnesses

We show Shelah&#39;s original creature forcing from 1984 strongly preserves tight mad families. In particular, answering questions of Fischer and Friedman and Friedman and Zdomskyy, we show the constellation $\aleph_1 = \mathfrak{a} < \mathfrak{s} = \aleph_2$ is consistent with the existence of a $Δ_3^1$ wellorder of the reals and tight mad families of sizes $\aleph_1, \aleph_2$ which are $Π_1^1, Π_2^1$-definable, respectively. Each of these projective definitions is of minimal possible complexity.

4 nodes3 linksoverview previewStrong Projective Witnesses
4 nodes3 links
Strong Projective Witnesses4 visible / 4 total nodes / 4 links
Co-authorshipAuthorshipAuthorshipTopic signalWStrong Projective Witnessespreprint / 2026AVera FischerResearcherAJulia MillhouseResearcherTmath.LO1661 works
PaperSignal 103 links

Strong Projective Witnesses

preprint / 2026

Open