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Theorems · Theorem · general topology

PartitionOfUnity.exists_isSubordinate

∀ {ι : Type u} {X : Type v} [inst : TopologicalSpace X] {s : Set X} [NormalSpace X] [ParacompactSpace X],
  IsClosed s → ∀ (U : ι → Set X), (∀ (i : ι), IsOpen (U i)) → s ⊆ ⋃ i, U i → ∃ f, f.IsSubordinate U

If X is a paracompact normal topological space and U is an open covering of a closed set s, then there exists a PartitionOfUnity ι X s that is subordinate to U.

Defined in
Mathlib.Topology.PartitionOfUnity
Cited by
1 results in Mathlib
Foundations
Depth 170 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
TopologicalSpaceNormalSpaceParacompactSpace

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