diff --git a/Mathlib/Topology/Compactness/CountablyCompact.lean b/Mathlib/Topology/Compactness/CountablyCompact.lean index d32142964c8b24..db91cd4c740d70 100644 --- a/Mathlib/Topology/Compactness/CountablyCompact.lean +++ b/Mathlib/Topology/Compactness/CountablyCompact.lean @@ -261,9 +261,9 @@ instance (priority := 50) [SequentialSpace E] [CountablyCompactSpace E] : · simp only [image_eq_iUnion, mem_Ici, iUnion_ge_eq_iUnion_nat_add _ (k + 1)] exact iUnion_mono fun i => subset_closure -/-- If `f : X → Y` is an embedding map, the image `f '' s` of a set `s` is sequentially compact +/-- If `f : X → Y` is an inducing map, the image `f '' s` of a set `s` is sequentially compact if and only if `s` is sequentially compact. -/ -theorem Topology.IsEmbedding.isSeqCompact_iff {f : E → F} (hf : IsEmbedding f) : +theorem Topology.IsInducing.isSeqCompact_iff {f : E → F} (hf : IsInducing f) : IsSeqCompact A ↔ IsSeqCompact (f '' A) where mp hA x hx := by choose y hy using hx @@ -358,10 +358,13 @@ theorem IsLindelof.isCompact (hA : IsCountablyCompact A) (hl : IsLindelof A) : · exact ⟨∅, by simp_all⟩ /-- A countably compact Lindelöf space is compact. -/ -theorem LindelofSpace.CompactSpace {X : Type*} [TopologicalSpace X] +theorem LindelofSpace.compactSpace {X : Type*} [TopologicalSpace X] [LindelofSpace X] [h : CountablyCompactSpace X] : CompactSpace X where isCompact_univ := isLindelof_univ.isCompact h.isCountablyCompact_univ +@[deprecated (since := "2026-05-19")] +alias LindelofSpace.CompactSpace := LindelofSpace.compactSpace + /-- In a Hereditarily Lindelöf space, a countably compact set is compact. -/ theorem IsCountablyCompact.isCompact [HereditarilyLindelofSpace E] (hA : IsCountablyCompact A) : IsCompact A :=