Source: J. Symbolic Logic
Volume 76, Issue 4
We show that Sacks' and Shoenfield's analogs of jump inversion fail
for both tt- and wtt-reducibilities in a strong way.
In particular we show that there is a Δ02 set B >tt ∅'
such that there is no c.e. set A with A' ≡wtt B.
We also show that there is a Σ02 set C
>tt ∅' such
that there is no Δ02 set D with D' ≡wtt C.
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