English

Reals n-generic relative to some perfect tree

Logic 2008-07-19 v2

Abstract

We say that a real X is n-generic relative to a perfect tree T if X is a path through T and for all Sigma^0_n (T) sets S, there exists a number k such that either X|k is in S or for all tau in T extending X|k we have tau is not in S. A real X is n-generic relative to some perfect tree if there exists such a T. We first show that for every number n all but countably many reals are n-generic relative to some perfect tree. Second, we show that proving this statement requires ZFC^- + ``There exist infinitely many iterates of the power set of the natural numbers''. Third, we prove that every finite iterate of the hyperjump, O^(n), is not 2-generic relative to any perfect tree and for every ordinal alpha below the least lambda such that sup_{beta < lambda} (beta th admissible) = lambda, the iterated hyperjump O^(alpha) is not 5-generic relative to any perfect tree. Finally, we demonstrate some necessary conditions for reals to be 1-generic relative to some perfect tree.

Keywords

Cite

@article{arxiv.math/0610306,
  title  = {Reals n-generic relative to some perfect tree},
  author = {Bernard A. Anderson},
  journal= {arXiv preprint arXiv:math/0610306},
  year   = {2008}
}

Comments

12 pages. Updated to final form (a few details added, minor errors corrected)

R2 v1 2026-07-22T17:43:57.773Z