Kazuyuki Tanaka

Learn More
By RCA 0 , we denote the system of second order arithmetic based on recursive comprehension axioms and Σ 0 1 induction. WKL 0 is defined to be RCA 0 plus weak König's lemma: every infinite tree of sequences of 0's and 1's has an infinite path. In this paper, we first show that for any countable model M of RCA 0 , there exists a count-able model M of WKL 0(More)