Aspects of the Turing jump
Theodore A. Slaman · Cambridge University Press eBooks · 2017
closure operators In our first application, we argue that the iterations of the Turing jump have a special role within relative definability. In the following definition, we are thinking of M as a function which maps X in 2 N to the set of those Y 's in 2 N which are definable from X (in some specific way).