Definability and Initial Segments of $c$-Degrees
Lubarsky, Robert S.
J. Symbolic Logic, Tome 53 (1988) no. 1, p. 1070-1081 / Harvested from Project Euclid
We combine two techniques of set theory relating to minimal degrees of constructibility. Jensen constructed a minimal real which is additionally a $\Pi^1_2$ singleton. Groszek built an initial segment of order type $1 + \alpha^\ast$, for any ordinal $\alpha$. This paper shows how to force a $\Pi^1_2$ singleton such that the $c$-degrees beneath it, all represented by reals, are of type $1 + \alpha^\ast$, for many ordinals $\alpha$. We also examine the definability $\alpha$ needs to be so represented by a real.
Publié le : 1988-12-14
Classification: 
@article{1183742782,
     author = {Lubarsky, Robert S.},
     title = {Definability and Initial Segments of $c$-Degrees},
     journal = {J. Symbolic Logic},
     volume = {53},
     number = {1},
     year = {1988},
     pages = { 1070-1081},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1183742782}
}
Lubarsky, Robert S. Definability and Initial Segments of $c$-Degrees. J. Symbolic Logic, Tome 53 (1988) no. 1, pp.  1070-1081. http://gdmltest.u-ga.fr/item/1183742782/