Documentation

Mathlib.Topology.Sets.Closeds

Closed sets #

We define a few types of closed sets in a topological space.

Main Definitions #

For a topological space α,

Closed sets #

structure TopologicalSpace.Closeds (α : Type u_4) [TopologicalSpace α] :
Type u_4

The type of closed subsets of a topological space.

  • carrier : Set α

    the carrier set, i.e. the points in this set

  • closed' : IsClosed self.carrier
Instances For

    See Note [custom simps projection].

    Equations
    Instances For
      theorem TopologicalSpace.Closeds.ext {α : Type u_2} [TopologicalSpace α] {s t : Closeds α} (h : ↑s = ↑t) :
      s = t
      theorem TopologicalSpace.Closeds.ext_iff {α : Type u_2} [TopologicalSpace α] {s t : Closeds α} :
      s = t ↔ ↑s = ↑t
      @[simp]
      theorem TopologicalSpace.Closeds.coe_mk {α : Type u_2} [TopologicalSpace α] (s : Set α) (h : IsClosed s) :
      ↑{ carrier := s, closed' := h } = s

      The closure of a set, as an element of TopologicalSpace.Closeds.

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        @[simp]

        The galois coinsertion between sets and opens.

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          • One or more equations did not get rendered due to their size.

          The type of closed sets is inhabited, with default element the empty set.

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          @[simp]
          theorem TopologicalSpace.Closeds.coe_sup {α : Type u_2} [TopologicalSpace α] (s t : Closeds α) :
          ↑(s ⊔ t) = ↑s ∪ ↑t
          @[simp]
          theorem TopologicalSpace.Closeds.coe_inf {α : Type u_2} [TopologicalSpace α] (s t : Closeds α) :
          ↑(s ⊓ t) = ↑s ∩ ↑t
          @[simp]
          @[simp]
          @[simp]
          theorem TopologicalSpace.Closeds.coe_sInf {α : Type u_2} [TopologicalSpace α] {S : Set (Closeds α)} :
          ↑(sInf S) = ⋂ i ∈ S, ↑i
          @[simp]
          @[simp]
          theorem TopologicalSpace.Closeds.coe_finset_sup {ι : Type u_1} {α : Type u_2} [TopologicalSpace α] (f : ι → Closeds α) (s : Finset ι) :
          ↑(s.sup f) = s.sup (SetLike.coe ∘ f)
          @[simp]
          theorem TopologicalSpace.Closeds.coe_finset_inf {ι : Type u_1} {α : Type u_2} [TopologicalSpace α] (f : ι → Closeds α) (s : Finset ι) :
          ↑(s.inf f) = s.inf (SetLike.coe ∘ f)
          @[simp]
          theorem TopologicalSpace.Closeds.mem_sInf {α : Type u_2} [TopologicalSpace α] {S : Set (Closeds α)} {x : α} :
          x ∈ sInf S ↔ ∀ s ∈ S, x ∈ s
          @[simp]
          theorem TopologicalSpace.Closeds.mem_iInf {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} {x : α} {s : ι → Closeds α} :
          x ∈ iInf s ↔ ∀ (i : ι), x ∈ s i
          @[simp]
          theorem TopologicalSpace.Closeds.coe_iInf {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} (s : ι → Closeds α) :
          ↑(⨅ (i : ι), s i) = ⋂ (i : ι), ↑(s i)
          theorem TopologicalSpace.Closeds.iInf_def {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} (s : ι → Closeds α) :
          ⨅ (i : ι), s i = { carrier := ⋂ (i : ι), ↑(s i), closed' := ⋯ }
          @[simp]
          theorem TopologicalSpace.Closeds.iInf_mk {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} (s : ι → Set α) (h : ∀ (i : ι), IsClosed (s i)) :
          ⨅ (i : ι), { carrier := s i, closed' := ⋯ } = { carrier := ⋂ (i : ι), s i, closed' := ⋯ }

          Closed sets in a topological space form a coframe.

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            The term of TopologicalSpace.Closeds α corresponding to a singleton.

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              @[simp]
              theorem TopologicalSpace.Closeds.coe_singleton {α : Type u_2} [TopologicalSpace α] [T1Space α] (x : α) :
              ↑(singleton x) = {x}
              @[simp]
              theorem TopologicalSpace.Closeds.mem_singleton {α : Type u_2} [TopologicalSpace α] [T1Space α] {a b : α} :
              a ∈ singleton b ↔ a = b

              The complement of a closed set as an open set.

              Equations
              • s.compl = { carrier := (↑s)ᶜ, is_open' := ⋯ }
              Instances For
                @[simp]
                theorem TopologicalSpace.Closeds.coe_compl {α : Type u_2} [TopologicalSpace α] (s : Closeds α) :
                ↑s.compl = (↑s)ᶜ

                The complement of an open set as a closed set.

                Equations
                • s.compl = { carrier := (↑s)ᶜ, closed' := ⋯ }
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                  @[simp]
                  theorem TopologicalSpace.Opens.coe_compl {α : Type u_2} [TopologicalSpace α] (s : Opens α) :
                  ↑s.compl = (↑s)ᶜ

                  TopologicalSpace.Closeds.compl as an OrderIso to the order dual of TopologicalSpace.Opens α.

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                    TopologicalSpace.Opens.compl as an OrderIso to the order dual of TopologicalSpace.Closeds α.

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                    • One or more equations did not get rendered due to their size.
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                      theorem TopologicalSpace.Closeds.coe_eq_singleton_of_isAtom {α : Type u_2} [TopologicalSpace α] [T0Space α] {s : Closeds α} (hs : IsAtom s) :
                      ∃ (a : α), ↑s = {a}
                      @[simp]
                      theorem TopologicalSpace.Closeds.isAtom_iff {α : Type u_2} [TopologicalSpace α] [T1Space α] {s : Closeds α} :
                      IsAtom s ↔ ∃ (x : α), s = singleton x

                      in a T1Space, atoms of TopologicalSpace.Closeds α are precisely the TopologicalSpace.Closeds.singletons.

                      theorem TopologicalSpace.Opens.isCoatom_iff {α : Type u_2} [TopologicalSpace α] [T1Space α] {s : Opens α} :
                      IsCoatom s ↔ ∃ (x : α), s = (Closeds.singleton x).compl

                      in a T1Space, coatoms of TopologicalSpace.Opens α are precisely complements of singletons: (TopologicalSpace.Closeds.singleton x).compl.

                      Clopen sets #

                      structure TopologicalSpace.Clopens (α : Type u_4) [TopologicalSpace α] :
                      Type u_4

                      The type of clopen sets of a topological space.

                      • carrier : Set α

                        the carrier set, i.e. the points in this set

                      • isClopen' : IsClopen self.carrier
                      Instances For
                        Equations

                        See Note [custom simps projection].

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                          Reinterpret a clopen as an open.

                          Equations
                          • s.toOpens = { carrier := ↑s, is_open' := ⋯ }
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                            @[simp]
                            theorem TopologicalSpace.Clopens.coe_toOpens {α : Type u_2} [TopologicalSpace α] (s : Clopens α) :
                            ↑s.toOpens = ↑s

                            Reinterpret a clopen as a closed.

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                              @[simp]
                              theorem TopologicalSpace.Clopens.ext {α : Type u_2} [TopologicalSpace α] {s t : Clopens α} (h : ↑s = ↑t) :
                              s = t
                              theorem TopologicalSpace.Clopens.ext_iff {α : Type u_2} [TopologicalSpace α] {s t : Clopens α} :
                              s = t ↔ ↑s = ↑t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_mk {α : Type u_2} [TopologicalSpace α] (s : Set α) (h : IsClopen s) :
                              ↑{ carrier := s, isClopen' := h } = s
                              @[simp]
                              theorem TopologicalSpace.Clopens.mem_mk {α : Type u_2} [TopologicalSpace α] {s : Set α} {x : α} {h : IsClopen s} :
                              x ∈ { carrier := s, isClopen' := h } ↔ x ∈ s
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                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_sup {α : Type u_2} [TopologicalSpace α] (s t : Clopens α) :
                              ↑(s ⊔ t) = ↑s ∪ ↑t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_inf {α : Type u_2} [TopologicalSpace α] (s t : Clopens α) :
                              ↑(s ⊓ t) = ↑s ∩ ↑t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_sdiff {α : Type u_2} [TopologicalSpace α] (s t : Clopens α) :
                              ↑(s \ t) = ↑s \ ↑t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_himp {α : Type u_2} [TopologicalSpace α] (s t : Clopens α) :
                              ↑(s ⇨ t) = ↑s ⇨ ↑t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_compl {α : Type u_2} [TopologicalSpace α] (s : Clopens α) :
                              ↑sᶜ = (↑s)ᶜ
                              instance TopologicalSpace.Clopens.instSProdProd {α : Type u_2} {β : Type u_3} [TopologicalSpace α] [TopologicalSpace β] :
                              SProd (Clopens α) (Clopens β) (Clopens (α × β))
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                              @[simp]
                              theorem TopologicalSpace.Clopens.mem_prod {α : Type u_2} {β : Type u_3} [TopologicalSpace α] [TopologicalSpace β] {s : Clopens α} {t : Clopens β} {x : α × β} :
                              x ∈ s ×ˢ t ↔ x.1 ∈ s ∧ x.2 ∈ t
                              @[simp]
                              theorem TopologicalSpace.Clopens.coe_finset_sup {ι : Type u_1} {α : Type u_2} [TopologicalSpace α] (s : Finset ι) (U : ι → Clopens α) :
                              ↑(s.sup U) = ⋃ i ∈ s, ↑(U i)

                              Irreducible closed sets #

                              The type of irreducible closed subsets of a topological space.

                              Instances For

                                See Note [custom simps projection].

                                Equations
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                                  theorem TopologicalSpace.IrreducibleCloseds.ext {α : Type u_2} [TopologicalSpace α] {s t : IrreducibleCloseds α} (h : ↑s = ↑t) :
                                  s = t
                                  @[simp]
                                  theorem TopologicalSpace.IrreducibleCloseds.coe_mk {α : Type u_2} [TopologicalSpace α] (s : Set α) (h : IsIrreducible s) (h' : IsClosed s) :
                                  ↑{ carrier := s, is_irreducible' := h, is_closed' := h' } = s

                                  The term of TopologicalSpace.IrreducibleCloseds α corresponding to a singleton.

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                                    The equivalence between IrreducibleCloseds α and {x : Set α // IsIrreducible x ∧ IsClosed x }.

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                                    • One or more equations did not get rendered due to their size.
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                                      @[simp]
                                      theorem TopologicalSpace.IrreducibleCloseds.equivSubtype_symm_apply {α : Type u_2} [TopologicalSpace α] (a : { x : Set α // IsIrreducible x ∧ IsClosed x }) :
                                      equivSubtype.symm a = { carrier := ↑a, is_irreducible' := ⋯, is_closed' := ⋯ }

                                      The equivalence between IrreducibleCloseds α and {x : Set α // IsClosed x ∧ IsIrreducible x }.

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                                      • One or more equations did not get rendered due to their size.
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                                        @[simp]
                                        theorem TopologicalSpace.IrreducibleCloseds.equivSubtype'_symm_apply {α : Type u_2} [TopologicalSpace α] (a : { x : Set α // IsClosed x ∧ IsIrreducible x }) :
                                        equivSubtype'.symm a = { carrier := ↑a, is_irreducible' := ⋯, is_closed' := ⋯ }