On a conjecture of Debs and Saint Raymond

2021/09/03 by Kwela, Adam
#FOS: Mathematics #Logic (math.LO)

paper · doi:10.48550/arxiv.2109.01516

Abstract

Borel separation rank of an analytic ideal I on ω is the minimal ordinal α<ω₁ such that there is S∈\bfΣ⁰_1+α with I⊆ S and I^⋆∩ S=∅, where I^⋆ is the filter dual to the ideal I. Answering in negative a question of G. Debs and J. Saint Raymond [Fund. Math. 204 (2009), no. 3], we construct a Borel ideal of rank >2 which does not contain an isomorphic copy of the ideal Fin³.

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