The Existence of an Ahmad Triple
نویسندگان
چکیده
We construct a so-called Ahmad triple in the Σ2enumeration degrees; that is, we construct three Σ2-sets A, B, and C such that A 6≤e B, B 6≤e C, ∀X (X <e A ⇒ X <e B) and ∀X (X <e B ⇒ X <e C). This constitutes a first step toward showing the ∀∃-theory of the Σ2-enumeration degrees to be decidable.
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