A proof of Shelah's eventual categoricity conjecture in universal classes

This is the title of a four-parts talk given at the CMU model theory seminar from March 14 to April 3, 2016. The talk presented the corresponding two papers.


Abstract elementary classes (AECs) are an axiomatic framework encompassing classes of models of an L∞, ω theory, as well as numerous algebraic examples. They were introduced by Saharon Shelah forty years ago. Shelah focused on generalizations of Morley’s categoricity theorem and conjectured the following eventual version: An AEC categorical in a high-enough cardinal is categorical on a tail of cardinals. I will present my proof of the conjecture for universal classes. They are a special case of AECs (studied by Shelah in a milestone 1987 paper) corresponding to classes of models of a universal L∞, ω theory.

I will initially discuss the proof with the additional assumption that the universal class satisfies the amalgamation property. In this case, the argument generalizes to AECs which have amalgamation, are tame (a locality property for orbital types isolated by Grossberg and VanDieren), and have primes over sets of the form Ma. Time permitting, I will discuss how to use Shelah’s structure theory of universal classes to remove the amalgamation assumption.