• Every countable model of set theory end-extends to a model of V = L

This theorem has popped up in my life a few times in the past week, and it’s one of the coolest results I know of, so I wanted to share it with the world.

Theorem (Barwise) Every countable transitive model of $\mathsf{ZF}$ has an end-extension to a model of $\mathsf{ZFC} + V = L$.

(I am currently in the progress of porting content over from my old site. If something is not yet here you should look there.)