English

Weak well orders and Fra\"iss\'e's conjecture

Logic 2023-04-07 v1

Abstract

The notion of well order admits an alternative definition in terms of embeddings between initial segments. We use the framework of reverse mathematics to investigate the logical strength of this definition and its connection with Fra\"iss\'e's conjecture, which has been proved by Laver. We also fill a small gap in Shore's proof that Fra\"iss\'e's conjecture implies arithmetic transfinite recursion over RCA0{\bf RCA}_0, by giving a new proof of Σ20\Sigma^0_2-induction.

Keywords

Cite

@article{arxiv.2304.03021,
  title  = {Weak well orders and Fra\"iss\'e's conjecture},
  author = {Anton Freund and Davide Manca},
  journal= {arXiv preprint arXiv:2304.03021},
  year   = {2023}
}
R2 v1 2026-06-28T09:52:44.011Z