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The weakness of finding descending sequences in ill-founded linear orders

Authors :
Goh, Jun Le
Pauly, Arno
Valenti, Manlio
Publication Year :
2024

Abstract

We prove that the Weihrauch degree of the problem of finding a bad sequence in a non-well quasi order ($\mathsf{BS}$) is strictly above that of finding a descending sequence in an ill-founded linear order ($\mathsf{DS}$). This corrects our mistaken claim in arXiv:2010.03840, which stated that they are Weihrauch equivalent. We prove that K\"onig's lemma $\mathsf{KL}$ and the problem $\mathsf{wList}_{2^{\mathbb{N}},\leq\omega}$ of enumerating a given non-empty countable closed subset of $2^\mathbb{N}$ are not Weihrauch reducible to $\mathsf{DS}$ either, resolving two main open questions raised in arXiv:2010.03840.

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2401.11807
Document Type :
Working Paper