Saturation conjecture for ideals extending the nonstationary ideal

Let κ=ν+\kappa=\nu^+, and let θ\theta be a regular infinite cardinal less than κ\kappa with θcf(ν)\theta\ne\operatorname{cf}(\nu). Let NSκEθκNS_\kappa\vert E^\kappa_\theta denote the restriction of the nonstationary ideal on κ\kappa to EθκE^\kappa_\theta, and let IκI_\kappa-κ+\kappa^+-saturated mean that the ideal has no antichain of size κ+\kappa^+ in its quotient Boolean algebra. Saturation conjecture. No κ\kappa-complete ideal on κ\kappa extending NSκEθκNS_\kappa\vert E^\kappa_\theta is IκI_\kappa-κ+\kappa^+-saturated.

The statement removes the cardinal-arithmetic hypothesis κ=2ν\kappa=2^\nu from the preceding result attributed to Shelah. The supplied text presents it as the paper's motivating conjecture and gives no resolution.

Sources & referencesView supporting material

Primary source

Pierre Matet, “Towers and clubs”, arXiv:1908.05336 (2019).

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