Consistency of separating the generalized null ideal from Cohen forcing

Let \boV\bo\mathbf V be a model and let \boκ\bo\kappa be a sufficiently strong cardinal. Write \boQκ\bo\mathbb Q_\kappa for the forcing notion associated with the generalized null ideal and \boCohenκ\bo\operatorname{Cohen}_\kappa for the forcing adding a κ\kappa-Cohen real. The cardinal \boadd(Qκ)\bo\operatorname{add}(\mathbb Q_\kappa) is the additivity of the corresponding ideal, and \bobκ\bo\mathfrak b_\kappa is the generalized bounding number.

Consistency conjecture. There exists a model \boV\bo\mathbf V such that

\boVadd(Qκ)>add(Cohenκ).\bo\mathbf V\models\operatorname{add}(\mathbb Q_\kappa)>\operatorname{add}(\operatorname{Cohen}_\kappa).

Since necessarily

\boVbκ=add(Cohenκ),\bo\mathbf V\models\mathfrak b_\kappa=\operatorname{add}(\operatorname{Cohen}_\kappa),

this is equivalently the consistency assertion

CON(add(Qκ)>bκ).\operatorname{CON}\bigl(\operatorname{add}(\mathbb Q_\kappa)>\mathfrak b_\kappa\bigr).

The claim asks whether the Bartoszyński–Raisonnier–Stern inequality can consistently fail for a sufficiently strong cardinal. The supplied text gives no resolution.

Sources & referencesView supporting material

Primary source

Thomas Baumhauer, Martin Goldstern and Saharon Shelah, “The Higher Cichoń Diagram”, arXiv:1806.08583 (2018).

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