Friday Set Theory Seminar (HUJI)

We shall meet Friday (December 12) in the Hebrew University math

department building, at 10 am.

Speaker: Juliette Kennedy (Helsinki)

Title: Change the logic, change the meaning? Inner models and extended logics.

Abstract: In his 1946 Princeton Bicentennial Lecture Gödel suggested the problem of finding a notion of definability for set theory which is “formalism free” in a sense similar to the notion of computable function — a notion which is very robust with respect to its various associated formalisms. One way to interpret this suggestion is to consider standard notions of definability in set theory, which are usually built over first order logic, and change the underlying logic. We show that constructibility is not very sensitive to the underlying logic, and the same goes for hereditary ordinal definability (or HOD). Some interesting intermediate models are discussed. This is joint work with Menachem Magidor and Jouko Väänänen.

See you there!