@@ -19,56 +19,56 @@ if either of the following equivalent conditions hold:
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provided that it is continuous on each `s ∈ S`.
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We use the first condition as the definition
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- (see `RestrictGenTopology ` in `Mathlib/Topology/Defs/Induced.lean`),
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+ (see `IsCoherentWith ` in `Mathlib/Topology/Defs/Induced.lean`),
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and provide the others as corollaries.
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## Main results
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- - `RestrictGenTopology .of_seq`: if `X` is a sequential space
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+ - `IsCoherentWith .of_seq`: if `X` is a sequential space
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and `S` contains all sets of the form `insert x (Set.range u)`,
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where `u : ℕ → X` is a sequence that converges to `x`,
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- then we have `RestrictGenTopology S`;
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+ then we have `IsCoherentWith S`;
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- - `RestrictGenTopology .isCompact_of_seq`: specialization of the previous lemma
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+ - `IsCoherentWith .isCompact_of_seq`: specialization of the previous lemma
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to the case `S = {K | IsCompact K}`.
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-/
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open Filter Set
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variable {X : Type *} [TopologicalSpace X] {S : Set (Set X)} {t : Set X} {x : X}
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- namespace Topology.RestrictGenTopology
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+ namespace Topology.IsCoherentWith
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- protected theorem isOpen_iff (hS : RestrictGenTopology S) :
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+ protected theorem isOpen_iff (hS : IsCoherentWith S) :
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IsOpen t ↔ ∀ s ∈ S, IsOpen ((↑) ⁻¹' t : Set s) :=
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⟨fun ht _ _ ↦ ht.preimage continuous_subtype_val, hS.1 t⟩
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- protected theorem isClosed_iff (hS : RestrictGenTopology S) :
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+ protected theorem isClosed_iff (hS : IsCoherentWith S) :
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IsClosed t ↔ ∀ s ∈ S, IsClosed ((↑) ⁻¹' t : Set s) := by
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simp only [← isOpen_compl_iff, hS.isOpen_iff, preimage_compl]
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protected theorem continuous_iff {Y : Type *} [TopologicalSpace Y] {f : X → Y}
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- (hS : RestrictGenTopology S) :
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+ (hS : IsCoherentWith S) :
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Continuous f ↔ ∀ s ∈ S, ContinuousOn f s :=
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⟨fun h _ _ ↦ h.continuousOn, fun h ↦ continuous_def.2 fun _u hu ↦ hS.isOpen_iff.2 fun s hs ↦
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hu.preimage <| (h s hs).restrict⟩
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theorem of_continuous_prop (h : ∀ f : X → Prop , (∀ s ∈ S, ContinuousOn f s) → Continuous f) :
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- RestrictGenTopology S where
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+ IsCoherentWith S where
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isOpen_of_forall_induced u hu := by
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simp only [continuousOn_iff_continuous_restrict, continuous_Prop] at *
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exact h _ hu
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theorem of_isClosed (h : ∀ t : Set X, (∀ s ∈ S, IsClosed ((↑) ⁻¹' t : Set s)) → IsClosed t) :
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- RestrictGenTopology S :=
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+ IsCoherentWith S :=
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⟨fun _t ht ↦ isClosed_compl_iff.1 <| h _ fun s hs ↦ (ht s hs).isClosed_compl⟩
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- protected theorem enlarge {T} (hS : RestrictGenTopology S) (hT : ∀ s ∈ S, ∃ t ∈ T, s ⊆ t) :
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- RestrictGenTopology T :=
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+ protected theorem enlarge {T} (hS : IsCoherentWith S) (hT : ∀ s ∈ S, ∃ t ∈ T, s ⊆ t) :
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+ IsCoherentWith T :=
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of_continuous_prop fun _f hf ↦ hS.continuous_iff.2 fun s hs ↦
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let ⟨t, htT, hst⟩ := hT s hs; (hf t htT).mono hst
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- protected theorem mono {T} (hS : RestrictGenTopology S) (hT : S ⊆ T) : RestrictGenTopology T :=
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+ protected theorem mono {T} (hS : IsCoherentWith S) (hT : S ⊆ T) : IsCoherentWith T :=
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hS.enlarge fun s hs ↦ ⟨s, hT hs, Subset.rfl⟩
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/-- If `X` is a sequential space
@@ -77,7 +77,7 @@ where `u : ℕ → X` is a sequence and `x` is its limit,
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then topology on `X` is generated by its restrictions to the sets of `S`. -/
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lemma of_seq [SequentialSpace X]
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(h : ∀ ⦃u : ℕ → X⦄ ⦃x : X⦄, Tendsto u atTop (𝓝 x) → insert x (range u) ∈ S) :
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- RestrictGenTopology S := by
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+ IsCoherentWith S := by
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refine of_isClosed fun t ht ↦ IsSeqClosed.isClosed fun u x hut hux ↦ ?_
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rcases isClosed_induced_iff.1 (ht _ (h hux)) with ⟨s, hsc, hst⟩
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rw [Subtype.preimage_val_eq_preimage_val_iff, Set.ext_iff] at hst
@@ -87,19 +87,19 @@ lemma of_seq [SequentialSpace X]
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simp_all
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/-- A sequential space is compactly generated. -/
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- lemma isCompact_of_seq [SequentialSpace X] : RestrictGenTopology {K : Set X | IsCompact K} :=
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+ lemma isCompact_of_seq [SequentialSpace X] : IsCoherentWith {K : Set X | IsCompact K} :=
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of_seq fun _u _x hux ↦ hux.isCompact_insert_range
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/-- If each point of the space has a neighborhood from the family `S`,
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then the topology is generated by its restrictions to the sets of `S`. -/
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- lemma of_nhds (h : ∀ x, ∃ s ∈ S, s ∈ 𝓝 x) : RestrictGenTopology S :=
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+ lemma of_nhds (h : ∀ x, ∃ s ∈ S, s ∈ 𝓝 x) : IsCoherentWith S :=
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of_continuous_prop fun _f hf ↦ continuous_iff_continuousAt.2 fun x ↦
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let ⟨s, hsS, hsx⟩ := h x
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(hf s hsS).continuousAt hsx
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/-- A weakly locally compact space is compactly generated. -/
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lemma isCompact_of_weaklyLocallyCompact [WeaklyLocallyCompactSpace X] :
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- RestrictGenTopology {K : Set X | IsCompact K} :=
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+ IsCoherentWith {K : Set X | IsCompact K} :=
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of_nhds exists_compact_mem_nhds
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- end Topology.RestrictGenTopology
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+ end Topology.IsCoherentWith
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