Chaitin Omega Numbers and Strong Reducibilities
Cristian S. Calude, André Nies · ResearchSpace (University of Auckland) · 1997
We prove that any Chaitin Ω number (i.e., the halting probability of a universal self-delimiting Turing machine) is wtt-complete, but not tt-complete. In this way we obtain a whole class of natural examples of wtt-complete but not tt-complete r.e. sets. The proof is direct and elementary.