Jaegers' recursive monotone fixed-point conjecture

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Let N{\mathcal{N}} denote Baire space. A partial ordering ⪯\preceq on N{\mathcal{N}} is Π10\Pi^0_1, every ⪯\preceq-chain has a least upper bound, and f:N×N→Nf:{\mathcal{N}}\times{\mathcal{N}}\to{\mathcal{N}} has sections fγ:N→Nf_\gamma:{\mathcal{N}}\to{\mathcal{N}}. Jaegers' conjecture. There is such a partial ordering and function ff satisfying: (i) ff is recursive; (ii) every section fγf_\gamma is monotone with respect to ⪯\preceq and therefore has a fixed point; and (iii) no fixed point of fγf_\gamma is HYP⁡(γ)\operatorname{HYP}(\gamma). The conjecture proposes a Baire-space analogue of the preceding non-uniformization result, overcoming the compactness obstruction that prevents the corresponding function on Cantor space from being recursive; the necessary modification of the ordering is left implicit.

References

Primary source

Vassilios Gregoriades, “On a Question of Jaegers”, arXiv:1905.09609 (2022).

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