The low2_2 supersets lattice conjecture

Let AA be a computably enumerable set. Write E\mathcal{E}^* for the lattice of all computably enumerable sets modulo finite sets, and let L(A)L^*(A) denote the lattice of supersets of AA modulo finite sets. A computably enumerable set AA is low2_2 when its second Turing jump satisfies ATA”\equiv_T\emptyset”. The low2_2 supersets lattice conjecture. If AA is low2_2, then

L(A)E.L^*(A)\cong \mathcal{E}^*.

Soare proved the analogous result for low computably enumerable sets, while Maass characterized effective isomorphism with E\mathcal{E}^* using semilow1.5_{1.5}. The conjecture asks whether the conclusion extends to all low2_2 computably enumerable sets and remains open.

Sources & referencesView supporting material

Primary source

Peter Cholak, Rodney Downey and Noam Greenberg, “Low_2 computably enumerable sets have hyperhypersimple supersets”, arXiv:2412.01939 (2025).

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