Mass problems and density
نویسندگان
چکیده
Recall that Ew is the lattice of Muchnik degrees of nonempty effectively compact sets in Euclidean space. We solve a long-standing open problem by proving that Ew is dense, i.e., satis es 8x8y (x < y ) 9z (x < z < y)). Our proof combines an oracle construction with hyperarithmetical theory.
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