Compactness step: if the closed normal subgroups satisfying \(M \sqcup K = \top\) are already stable under finite intersections, then they are stable under arbitrary intersections.
Source context 2 commands
Surrounding namespaces, section variables, and local commands at this declaration.
namespace ProCGroups.NormalSubgroups
universe utheorem maximal_open_normal_intersections_compactness_step
{G : Type u} [Group G] [TopologicalSpace G] [IsTopologicalGroup G] [CompactSpace G]
(K : Subgroup G) [K.Normal] (hKclosed : IsClosed (K : Set G))
(𝓜 : Set (Subgroup G))
(hMclosed : ∀ M ∈ 𝓜, IsClosed (M : Set G))
(hfinite :
∀ S : Set (Subgroup G), S.Finite → S ⊆ 𝓜 → sInf S ⊔ K = ⊤) :
sInf 𝓜 ⊔ K = ⊤