Uniform van Lambalgen's theorem fails for computable randomness

Abstract

We show that there exists a bitsequence that is not computably random for which its odd bits are computably random and its even bits are computably random relative to the odd bits. This implies that the uniform variant of van Lambalgen's theorem fails for computable randomness. (The other direction of van Lambalgen's theorem is known to hold in this case, and known to fail for the non-uniform variant.)