Doing mathematics in 3rd order arithmetic

Michael Rathjen, University of Leeds. Part of the proofs, constructions and computations seminar series.

I'll say a little bit more about developing mathematics in the small set-theoretic world known as Jensen's J_2.  Then I'll turn to another paper of Weaver's that looks at mathematics from the viewpoint of semi-intuitionistic third order arithmetic.  It'll be interesting to gauge the proof-theoretic strength of the latter.