Documentation

Mathlib.Topology.Sets.Compacts

Compact sets #

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

Main Definitions #

For a topological space α,

Compact sets #

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

The type of compact sets of a topological space.

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    Equations
    • TopologicalSpace.Compacts.instSetLikeCompacts = { coe := TopologicalSpace.Compacts.carrier, coe_injective' := }

    See Note [custom simps projection].

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      @[simp]
      theorem TopologicalSpace.Compacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : Set α) (h : IsCompact s) :
      { carrier := s, isCompact' := h } = s
      Equations
      • TopologicalSpace.Compacts.instSupCompacts = { sup := fun (s t : TopologicalSpace.Compacts α) => { carrier := s t, isCompact' := } }
      Equations
      • TopologicalSpace.Compacts.instInfCompacts = { inf := fun (s t : TopologicalSpace.Compacts α) => { carrier := s t, isCompact' := } }
      Equations
      • TopologicalSpace.Compacts.instTopCompacts = { top := { carrier := Set.univ, isCompact' := } }
      Equations
      • TopologicalSpace.Compacts.instBotCompacts = { bot := { carrier := , isCompact' := } }
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      Equations
      Equations
      • TopologicalSpace.Compacts.instOrderBotCompactsToLEToPreorderToPartialOrderInstSemilatticeSupCompacts = OrderBot.lift SetLike.coe
      Equations
      • TopologicalSpace.Compacts.instBoundedOrderCompactsToLEToPreorderToPartialOrderInstSemilatticeSupCompacts = BoundedOrder.lift SetLike.coe

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

      Equations
      • TopologicalSpace.Compacts.instInhabitedCompacts = { default := }
      @[simp]
      @[simp]
      theorem TopologicalSpace.Compacts.coe_top {α : Type u_1} [TopologicalSpace α] [CompactSpace α] :
      = Set.univ
      @[simp]
      theorem TopologicalSpace.Compacts.coe_finset_sup {α : Type u_1} [TopologicalSpace α] {ι : Type u_4} {s : Finset ι} {f : ιTopologicalSpace.Compacts α} :
      (Finset.sup s f) = Finset.sup s fun (i : ι) => (f i)

      The image of a compact set under a continuous function.

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      Instances For
        @[simp]
        theorem TopologicalSpace.Compacts.coe_map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] {f : αβ} (hf : Continuous f) (s : TopologicalSpace.Compacts α) :

        A homeomorphism induces an equivalence on compact sets, by taking the image.

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          The image of a compact set under a homeomorphism can also be expressed as a preimage.

          The product of two TopologicalSpace.Compacts, as a TopologicalSpace.Compacts in the product space.

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            Nonempty compact sets #

            The type of nonempty compact sets of a topological space.

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              See Note [custom simps projection].

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                Reinterpret a nonempty compact as a closed set.

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                  @[simp]
                  theorem TopologicalSpace.NonemptyCompacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : TopologicalSpace.Compacts α) (h : Set.Nonempty s.carrier) :
                  { toCompacts := s, nonempty' := h } = s
                  Equations
                  • TopologicalSpace.NonemptyCompacts.instSupNonemptyCompacts = { sup := fun (s t : TopologicalSpace.NonemptyCompacts α) => { toCompacts := s.toCompacts t.toCompacts, nonempty' := } }
                  Equations
                  • TopologicalSpace.NonemptyCompacts.instTopNonemptyCompacts = { top := { toCompacts := , nonempty' := } }
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                  Equations
                  • TopologicalSpace.NonemptyCompacts.instOrderTopNonemptyCompactsToLEToPreorderToPartialOrderInstSemilatticeSupNonemptyCompacts = OrderTop.lift SetLike.coe
                  @[simp]

                  In an inhabited space, the type of nonempty compact subsets is also inhabited, with default element the singleton set containing the default element.

                  Equations
                  • TopologicalSpace.NonemptyCompacts.instInhabitedNonemptyCompacts = { default := { toCompacts := { carrier := {default}, isCompact' := }, nonempty' := } }

                  The product of two TopologicalSpace.NonemptyCompacts, as a TopologicalSpace.NonemptyCompacts in the product space.

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                    Positive compact sets #

                    The type of compact sets with nonempty interior of a topological space. See also TopologicalSpace.Compacts and TopologicalSpace.NonemptyCompacts.

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                      See Note [custom simps projection].

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                        Reinterpret a positive compact as a nonempty compact.

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                          @[simp]
                          theorem TopologicalSpace.PositiveCompacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : TopologicalSpace.Compacts α) (h : Set.Nonempty (interior s.carrier)) :
                          { toCompacts := s, interior_nonempty' := h } = s
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                          • One or more equations did not get rendered due to their size.
                          Equations
                          • TopologicalSpace.PositiveCompacts.instTopPositiveCompacts = { top := { toCompacts := , interior_nonempty' := } }
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                          Equations
                          • TopologicalSpace.PositiveCompacts.instOrderTopPositiveCompactsToLEToPreorderToPartialOrderInstSemilatticeSupPositiveCompacts = OrderTop.lift SetLike.coe
                          @[simp]

                          The image of a positive compact set under a continuous open map.

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                            @[simp]
                            theorem TopologicalSpace.PositiveCompacts.coe_map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] {f : αβ} (hf : Continuous f) (hf' : IsOpenMap f) (s : TopologicalSpace.PositiveCompacts α) :
                            Equations
                            • TopologicalSpace.PositiveCompacts.instInhabitedPositiveCompacts = { default := }

                            In a nonempty locally compact space, there exists a compact set with nonempty interior.

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                            • =

                            The product of two TopologicalSpace.PositiveCompacts, as a TopologicalSpace.PositiveCompacts in the product space.

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                              Compact open sets #

                              The type of compact open sets of a topological space. This is useful in non Hausdorff contexts, in particular spectral spaces.

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                                See Note [custom simps projection].

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                                  Reinterpret a compact open as an open.

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                                    Reinterpret a compact open as a clopen.

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                                      @[simp]
                                      theorem TopologicalSpace.CompactOpens.coe_mk {α : Type u_1} [TopologicalSpace α] (s : TopologicalSpace.Compacts α) (h : IsOpen s.carrier) :
                                      { toCompacts := s, isOpen' := h } = s
                                      Equations
                                      • TopologicalSpace.CompactOpens.instSupCompactOpens = { sup := fun (s t : TopologicalSpace.CompactOpens α) => { toCompacts := s.toCompacts t.toCompacts, isOpen' := } }
                                      Equations
                                      • TopologicalSpace.CompactOpens.instInfCompactOpens = { inf := fun (U V : TopologicalSpace.CompactOpens α) => { toCompacts := { carrier := U V, isCompact' := }, isOpen' := } }
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                                      Equations
                                      • TopologicalSpace.CompactOpens.instTopCompactOpens = { top := { toCompacts := , isOpen' := } }
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                                      • TopologicalSpace.CompactOpens.instBotCompactOpens = { bot := { toCompacts := , isOpen' := } }
                                      Equations
                                      • One or more equations did not get rendered due to their size.
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                                      • TopologicalSpace.CompactOpens.instHasComplCompactOpens = { compl := fun (s : TopologicalSpace.CompactOpens α) => { toCompacts := { carrier := (s), isCompact' := }, isOpen' := } }
                                      Equations
                                      Equations
                                      • TopologicalSpace.CompactOpens.instOrderBotCompactOpensToLEToPreorderToPartialOrderInstSemilatticeSupCompactOpens = OrderBot.lift SetLike.coe
                                      Equations
                                      Equations
                                      • TopologicalSpace.CompactOpens.instBoundedOrderCompactOpensToLEToPreorderToPartialOrderInstSemilatticeSupCompactOpens = BoundedOrder.lift SetLike.coe
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                                      @[simp]
                                      Equations
                                      • TopologicalSpace.CompactOpens.instInhabitedCompactOpens = { default := }
                                      @[simp]
                                      theorem TopologicalSpace.CompactOpens.map_toCompacts {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : αβ) (hf : Continuous f) (hf' : IsOpenMap f) (s : TopologicalSpace.CompactOpens α) :
                                      (TopologicalSpace.CompactOpens.map f hf hf' s).toCompacts = TopologicalSpace.Compacts.map f hf s.toCompacts

                                      The image of a compact open under a continuous open map.

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                                        @[simp]
                                        theorem TopologicalSpace.CompactOpens.coe_map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] {f : αβ} (hf : Continuous f) (hf' : IsOpenMap f) (s : TopologicalSpace.CompactOpens α) :
                                        (TopologicalSpace.CompactOpens.map f hf hf' s) = f '' s
                                        theorem TopologicalSpace.CompactOpens.map_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} [TopologicalSpace α] [TopologicalSpace β] [TopologicalSpace γ] (f : βγ) (g : αβ) (hf : Continuous f) (hg : Continuous g) (hf' : IsOpenMap f) (hg' : IsOpenMap g) (K : TopologicalSpace.CompactOpens α) :

                                        The product of two TopologicalSpace.CompactOpens, as a TopologicalSpace.CompactOpens in the product space.

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