Debs–Saint Raymond rank characterization conjecture for analytic ideals

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Let I\mathcal{I} be an analytic ideal. For 0<α<ω10<\alpha<\omega_1, let rk⁡(I)\operatorname{rk}(\mathcal{I}) denote the least β<ω1\beta<\omega_1 such that some Σ1+β0\boldsymbol{\Sigma}^0_{1+\beta} set separates I\mathcal{I} from its filter dual, and let Finα\mathrm{Fin}_\alpha be the ideal of rank α\alpha. Say that an ideal contains an isomorphic copy of Finα\mathrm{Fin}_\alpha if Finα⊑I\mathrm{Fin}_\alpha\sqsubseteq\mathcal{I} in the sense defined above.

Debs–Saint Raymond conjecture. For every analytic ideal I\mathcal{I} and 0<α<ω10<\alpha<\omega_1,

rk⁡(I)≥α⟺Finα⊑I.\operatorname{rk}(\mathcal{I})\geq\alpha\quad\Longleftrightarrow\quad \mathrm{Fin}_\alpha\sqsubseteq\mathcal{I}.

This conjecture proposes a combinatorial characterization of the Borel separation rank of analytic ideals: having rank at least α\alpha should be equivalent to containing the canonical ideal Finα\mathrm{Fin}_\alpha up to an isomorphic copy. The source presents it as a conjecture of Debs and Saint Raymond; no resolution is supplied here.

References

Primary source

Adam Kwela, “On a conjecture of Debs and Saint Raymond”, arXiv:2109.01516 (2025).

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