Limits on jump inversion for strong reducibilities
نویسندگان
چکیده
We show that Sacks’ and Shoenfield’s analogs of jump inversion fail for both ttand wttreducibilities in a strong way. In particular we show that there is a ∆2 set B >tt ∅ ′ such that there is no c.e. set A with A′ ≡wtt B . We also show that there is a Σ 0 2 set C >tt ∅ ′ such that there is no ∆2 set D with D′ ≡wtt C . §
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ورودعنوان ژورنال:
- J. Symb. Log.
دوره 76 شماره
صفحات -
تاریخ انتشار 2011