On a problem of Cooper and Epstein

Abstract

In “Bounding minimal degrees by computably enumerable degrees” by A. Li and D. Yang, (this Journal, \cite{LY}), the authors prove that there exist non-computable computably enumerable degrees c > a > z such that any minimal degree m being below c is also below a. We analyze the proof of their result and show that the proof contains a mistake. Instead we give a proof for the opposite result.