English

Disjoint Borel Functions

Logic 2017-08-24 v3

Abstract

For each aRa \in \mathbb{R}, we define a Borel function fa:RRf_a : \mathbb{R} \to \mathbb{R} which encodes aa in a certain sense. We show that for each Borel g:RRg : \mathbb{R} \to \mathbb{R}, fag=f_a \cap g = \emptyset implies aΔ11(c)a \in \Delta^1_1(c) where cc is any code for gg. We generalize this theorem for gg in larger pointclasses Γ\Gamma. Specifically, if Γ=Δ21\Gamma = \mathbf{\Delta}^1_2, then aL[c]a \in L[c]. Also for all nωn \in \omega, if Γ=Δ3+n1\Gamma = \mathbf{\Delta}^1_{3 + n}, then aM1+n(c)a \in \mathcal{M}_{1 + n}(c).

Keywords

Cite

@article{arxiv.1408.4200,
  title  = {Disjoint Borel Functions},
  author = {Dan Hathaway},
  journal= {arXiv preprint arXiv:1408.4200},
  year   = {2017}
}

Comments

15 pages

R2 v1 2026-06-22T05:32:53.436Z