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arxiv: 0901.3876 · v2 · pith:7P5JV57Xnew · submitted 2009-01-25 · 🧮 math.LO

Lattice initial segments of the Turing degrees

classification 🧮 math.LO
keywords degreesturingbelowlatticesprincipalsigma-0-3abovebounded
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We characterize the isomorphism types of principal ideals of the Turing degrees below 0' that are lattices as the lattices with a Sigma-0-3 presentation, by showing that each Sigma-0-3 presentable bounded upper semilattice is isomorphic to such a principal ideal. We get a similar result for the Turing degrees below any degree above 0".

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