Comparing DNR and WWKL
Klaus Ambos‐Spies, Bjørn Kjos-Hanssen, Steffen Lempp, Theodore A · 2004
Abstract. In Reverse Mathematics, the axiom system DNR, asserting the existence of diagonally non-recursive functions, is strictly weaker than WWKL0 (weak weak König’s Lemma). §1. Introduction. Reverse mathematics is a branch of proof theory which involves proving the equivalence of mathematical theorems with certain collec-tions of axioms over a weaker base theory. In the form adopted by Harvey Friedman (see, e.g., [3]) and Stephen G. Simpson, expounded in the monograph [9] and numerous papers, it involves formulating “countable mathematics ” in