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

  • isClosed' : IsClosed self.carrier
Instances For
    @[deprecated TopologicalSpace.Closeds.isClosed (since := "2025-04-20")]

    Alias of TopologicalSpace.Closeds.isClosed.

    See Note [custom simps projection].

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      @[simp]
      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, isClosed' := h } = s
      @[simp]
      theorem TopologicalSpace.Closeds.mem_mk {α : Type u_2} [TopologicalSpace α] {s : Set α} {hs : IsClosed s} {x : α} :
      x { carrier := s, isClosed' := hs } x s

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

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        @[simp]
        @[simp]
        theorem TopologicalSpace.Closeds.closure_le {α : Type u_2} [TopologicalSpace α] {s : Set α} {t : Closeds α} :

        The galois insertion between sets and closeds.

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          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) :
          (st) = s t
          @[simp]
          theorem TopologicalSpace.Closeds.coe_inf {α : Type u_2} [TopologicalSpace α] (s t : Closeds α) :
          (st) = s t
          @[simp]
          @[simp]
          @[simp]
          theorem TopologicalSpace.Closeds.coe_sInf {α : Type u_2} [TopologicalSpace α] {S : Set (Closeds α)} :
          (sInf S) = iS, i
          @[simp]
          @[simp]
          theorem TopologicalSpace.Closeds.coe_finset_sup {ι : Type u_1} {α : Type u_2} [TopologicalSpace α] (f : ιCloseds 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 : ιCloseds 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 sS, x s
          @[simp]
          theorem TopologicalSpace.Closeds.mem_iInf {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} {x : α} {s : ιCloseds 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 : ιCloseds 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 : ιCloseds α) :
          ⨅ (i : ι), s i = { carrier := ⋂ (i : ι), (s i), isClosed' := }
          @[simp]
          theorem TopologicalSpace.Closeds.iInf_mk {α : Type u_2} [TopologicalSpace α] {ι : Sort u_4} (s : ιSet α) (h : ∀ (i : ι), IsClosed (s i)) :
          ⨅ (i : ι), { carrier := s i, isClosed' := } = { carrier := ⋂ (i : ι), s i, isClosed' := }

          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
              def TopologicalSpace.Closeds.preimage {α : Type u_2} {β : Type u_3} [TopologicalSpace α] [TopologicalSpace β] (s : Closeds β) {f : αβ} (hf : Continuous f) :

              The preimage of a closed set under a continuous map.

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                @[simp]
                theorem TopologicalSpace.Closeds.coe_preimage {α : Type u_2} {β : Type u_3} [TopologicalSpace α] [TopologicalSpace β] (s : Closeds β) {f : αβ} (hf : Continuous f) :
                (s.preimage hf) = f ⁻¹' s

                The complement of a closed set as an open set.

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                  @[simp]
                  theorem TopologicalSpace.Closeds.coe_compl {α : Type u_2} [TopologicalSpace α] (s : Closeds α) :
                  s.compl = (↑s)

                  The complement of an open set as a closed set.

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                    @[simp]
                    theorem TopologicalSpace.Opens.coe_compl {α : Type u_2} [TopologicalSpace α] (s : Opens α) :
                    s.compl = (↑s)

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

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                    • One or more equations did not get rendered due to their size.
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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
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                          See Note [custom simps projection].

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                            Reinterpret a clopen as an 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) :
                                (st) = s t
                                @[simp]
                                theorem TopologicalSpace.Clopens.coe_inf {α : Type u_2} [TopologicalSpace α] (s t : Clopens α) :
                                (st) = 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) :
                                s = (↑s)
                                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 : ιClopens α) :
                                (s.sup U) = is, (U i)
                                @[simp]
                                theorem TopologicalSpace.Clopens.coe_disjoint {α : Type u_2} [TopologicalSpace α] {s t : Clopens α} :
                                Disjoint s t Disjoint s t

                                Irreducible closed sets #

                                The type of irreducible closed subsets of a topological space.

                                Instances For

                                  See Note [custom simps projection].

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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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                                        @[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' := }