English

A note on fragments of uniform reflection in second order arithmetic

Logic 2022-07-26 v1

Abstract

We consider fragments of uniform reflection for formulas in the analytic hierarchy over theories of second order arithmetic. The main result is that for any second order arithmetic theory T0T_0 extending RCA0{\sf RCA}_0 and axiomatizable by a Πk+21\Pi^1_{k+2} sentence, and for any nk+1n\geq k+1, T0+RFNΠn+21(T) = T0+TIΠn1(ε0), T_0+ \mathrm{RFN}_{\varPi^1_{n+2}}(T) \ = \ T_0 + \mathrm{TI}_{\varPi^1_n}(\varepsilon_0), T0+RFNΣn+11(T) = T0+TIΠn1(ε0), T_0+ \mathrm{RFN}_{\varSigma^1_{n+1}}(T) \ = \ T_0+ \mathrm{TI}_{\varPi^1_n}(\varepsilon_0)^{-}, where TT is T0T_0 augmented with full induction, and TIΠn1(ε0)\mathrm{TI}_{\varPi^1_n}(\varepsilon_0)^{-} denotes the schema of transfinite induction up to ε0\varepsilon_0 for Πn1\varPi^1_n formulas without set parameters.

Keywords

Cite

@article{arxiv.2207.11693,
  title  = {A note on fragments of uniform reflection in second order arithmetic},
  author = {Emanuele Frittaion},
  journal= {arXiv preprint arXiv:2207.11693},
  year   = {2022}
}
R2 v1 2026-06-25T01:10:43.838Z