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LeanPool.PCFTheory.Background.Cofinality

Cofinality results for indexed suprema #

A more general universe version of iSup_lt_ord_lift and a related corollary phrased in terms of Iio.

theorem Ordinal.iSup_lt_ord_lift' {ι : Type v} {f : ιOrdinal.{u}} {c : Ordinal.{u}} ( : Cardinal.lift.{u, v} (Cardinal.mk ι) < Cardinal.lift.{v, u} c.cof) :
(∀ (i : ι), f i < c)iSup f < c

A version of lift_iSup_lt_of_lt_cof with more general universes.

theorem Ordinal.iSup_Iio_lt_ord {δ : Ordinal.{u}} { : Ordinal.{v}} {f : (Set.Iio )Ordinal.{u}} (hf : ∀ (i : (Set.Iio )), f i < δ) (hcard : Cardinal.lift.{u, v} .card < Cardinal.lift.{v, u} δ.cof) :
iSup f < δ