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

This is the title of a talk given at the 2016 Logic Colloquium (University of Leeds) on August 4, 2016. The talk presented the corresponding two papers. Here are the slides.


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.

The proof combines Shelah's earlier work on universal classes with a study of AECs that have amalgamation and are tame (a locality property isolated by Grossberg and VanDieren which says roughly that orbital types are determined by their small restrictions).