ABSTRACT

We denote by / -1(21) the set f ~ l (R\) 0 · · · 0 f ~ l (Rfc). In particular, if / = λχ · x, then f ~ l (21) will be denoted by 2)(21).

Next we define for every recursive ordinal a the relatively a-intrinsic sets. Given a set D of natural numbers and a recursive ordinal a , by D ^ we shall denote the α -th enumeration jump of D. The exact definition will be given in the next section.