The Journal of Symbolic Logic

Research Article

Comparing DNR and WWKL

Klaus Ambos-Spiesa1, Bjørn Kjos-Hanssena2, Steffen Lemppa3 and Theodore A. Slamana4

a1 Mathematisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany, E-mail:

a2 Department of Mathematics, University of Connecticut, Storrs, Connecticut 06269-3009, USA, E-mail:

a3 Department of Mathematics, University of Wisconsin, Madison, Wisconsin 53706-1388, USA, E-mail:

a4 Department of Mathematics, The University of California, Berkeley, California 94720-3840, USA, E-mail:


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).

(Received February 03 2004)

(Revised April 04 2003)

Key words and phrases

  • reverse mathematics;
  • diagonally non-recursive functions;
  • Turing degrees