PSU Mark
Eberly College of Science Mathematics Department

Meeting Details

For more information about this meeting, contact Jan Reimann, Stephen Simpson.

Title:Cone Avoidance for Ramsey's theorem for pairs
Seminar:Logic Seminar
Speaker:Keita Yokoyama, Tokyo Institute of Technology and Pennsylvania State University
Determining the strength of Ramsey's theorem for pairs (RT^2_2) is a long standing problem in Computability Theory and Reverse Mathematics. The following two theorems are the significant contributions to this problem. In 1990s, Seetapun proved the cone avoidance theorem for Ramsey's theorem for pairs, which implies that RT^2_2 is strictly weaker than ACA_0. In 2001, Cholak, Jockusch and Slaman constructed a low_2 omega-model of RT^2_2 by using Mathias forcing, and showed that the first-order part of RT^2_2 is weaker than the system of Sigma_2-induction. In this talk, I will introduce another proof of Seetapun's theorem given by Dzhafarov and Jockusch, which is based on Mathias forcing used for the latter theorem.

Room Reservation Information

Room Number:MB315
Date:11 / 29 / 2011
Time:02:30pm - 03:45pm