From Cut Elimination to Pi^1_1-Comprehension

Anton Freund, University of Leeds. Part of the logic seminar series.

In the first half of my talk I will introduce some concepts of ordinal analysis.  In the second half I will explain how these concepts can be "lifted" to the domain of reverse mathematics. Specifically, I will present a "type-two well-ordering principle" that is equivalent to Pi^1_1-comprehension.