Hanf numbers for Extendibility and related phenomena
arXiv:2111.01704
Abstract
This paper contains portions of Baldwin's talk at the Set Theory and Model Theory Conference (Institute for Research in Fundamental Sciences, Tehran, October 2015) and a detailed proof that in a suitable extension of ZFC, there is a complete sentence of that has maximal models in cardinals cofinal in the first measurable cardinal and, of course, never again.
26 pages