Low${}_2$ computably enumerable sets have hyperhypersimple supersets

Peter Cholak, Rodney Downey, Noam Greenberg

A longstanding question is to characterize the lattice of supersets (modulo finite sets), ${\mathcal{L}}^{\ast }(A)$, of a low${}_2$ computably enumerable (c.e.) set. The conjecture is that…