Event Detail
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Fri Apr 8, 2016–Sat Apr 9, 2016 20 Barrows 11:10 PM–1 AM |
Alfred Tarski Lectures William W. Tait (Professor Emeritus, Department of Philosophy and CHSS, University of Chicago) Cut-Elimination for Subsystems of Classical Second-Order Number Theory: Cut-Elimination for Π_1^1 − CA with the ω-Rule—and Beyond(?) |
I will present a simplification of the proof of cut-eliminability of Gaisi Takeuti and Mariko Yasugi for this system. In particular, I will avoid the use of Takeuti’s ordinal diagrams. (I do use the finite part of the Veblen hierarchy, though.) Given time and sufficient conviction, I may speak about the possibility of extending the result to Π_2^1 − CA and beyond.