This post is a link to https://arxiv.org/abs/1707.04660

With John Clemens and Samuel Dworetzky.

Abstract: We study the complexity of the classification problem for countable models of set theory (ZFC). We prove that the classification of arbitrary countable models of ZFC is Borel complete, meaning that it is as complex as it can conceivably be. We then give partial results concerning the classification of countable well-founded models of ZFC.