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.

  • carrier : Set α

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

  • isCompact' : IsCompact self.carrier
Instances For

    See Note [custom simps projection].

    Equations
      Instances For
        theorem TopologicalSpace.Compacts.ext {α : Type u_1} [TopologicalSpace α] {s t : Compacts α} (h : s = t) :
        s = t
        theorem TopologicalSpace.Compacts.ext_iff {α : Type u_1} [TopologicalSpace α] {s t : Compacts α} :
        s = t s = t
        @[simp]
        theorem TopologicalSpace.Compacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : Set α) (h : IsCompact s) :
        { carrier := s, isCompact' := h } = s

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

        Equations
          @[simp]
          theorem TopologicalSpace.Compacts.coe_sup {α : Type u_1} [TopologicalSpace α] (s t : Compacts α) :
          (st) = s t
          @[simp]
          theorem TopologicalSpace.Compacts.coe_inf {α : Type u_1} [TopologicalSpace α] [T2Space α] (s t : Compacts α) :
          (st) = s t
          @[simp]
          theorem TopologicalSpace.Compacts.coe_finset_sup {α : Type u_1} [TopologicalSpace α] {ι : Type u_4} {s : Finset ι} {f : ιCompacts α} :
          (s.sup f) = s.sup fun (i : ι) => (f i)
          def TopologicalSpace.Compacts.map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : αβ) (hf : Continuous f) (K : Compacts α) :

          The image of a compact set under a continuous function.

          Equations
            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 : Compacts α) :
              (Compacts.map f hf s) = f '' s
              @[simp]
              theorem TopologicalSpace.Compacts.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) (K : Compacts α) :
              Compacts.map (f g) K = Compacts.map f hf (Compacts.map g hg K)

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

              Equations
                Instances For
                  @[simp]
                  theorem TopologicalSpace.Compacts.equiv_symm_apply {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : α ≃ₜ β) (K : Compacts β) :
                  @[simp]
                  theorem TopologicalSpace.Compacts.equiv_apply {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : α ≃ₜ β) (K : Compacts α) :
                  (Compacts.equiv f) K = Compacts.map f K
                  @[simp]
                  theorem TopologicalSpace.Compacts.equiv_trans {α : Type u_1} {β : Type u_2} {γ : Type u_3} [TopologicalSpace α] [TopologicalSpace β] [TopologicalSpace γ] (f : α ≃ₜ β) (g : β ≃ₜ γ) :
                  theorem TopologicalSpace.Compacts.coe_equiv_apply_eq_preimage {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : α ≃ₜ β) (K : Compacts α) :
                  ((Compacts.equiv f) K) = f.symm ⁻¹' K

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

                  def TopologicalSpace.Compacts.prod {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (K : Compacts α) (L : Compacts β) :
                  Compacts (α × β)

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

                  Equations
                    Instances For
                      @[simp]
                      theorem TopologicalSpace.Compacts.coe_prod {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (K : Compacts α) (L : Compacts β) :
                      (K.prod L) = K ×ˢ L

                      Nonempty compact sets #

                      The type of nonempty compact sets of a topological space.

                      Instances For

                        See Note [custom simps projection].

                        Equations
                          Instances For

                            Reinterpret a nonempty compact as a closed set.

                            Equations
                              Instances For
                                theorem TopologicalSpace.NonemptyCompacts.ext {α : Type u_1} [TopologicalSpace α] {s t : NonemptyCompacts α} (h : s = t) :
                                s = t
                                @[simp]
                                theorem TopologicalSpace.NonemptyCompacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : Compacts α) (h : s.carrier.Nonempty) :
                                { toCompacts := s, nonempty' := h } = s
                                @[simp]
                                theorem TopologicalSpace.NonemptyCompacts.coe_sup {α : Type u_1} [TopologicalSpace α] (s t : NonemptyCompacts α) :
                                (st) = s t

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

                                Equations

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

                                  Equations
                                    Instances For
                                      @[simp]
                                      theorem TopologicalSpace.NonemptyCompacts.coe_prod {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (K : NonemptyCompacts α) (L : NonemptyCompacts β) :
                                      (K.prod L) = K ×ˢ L

                                      Positive compact sets #

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

                                      Instances For

                                        See Note [custom simps projection].

                                        Equations
                                          Instances For

                                            Reinterpret a positive compact as a nonempty compact.

                                            Equations
                                              Instances For
                                                theorem TopologicalSpace.PositiveCompacts.ext {α : Type u_1} [TopologicalSpace α] {s t : PositiveCompacts α} (h : s = t) :
                                                s = t
                                                @[simp]
                                                theorem TopologicalSpace.PositiveCompacts.coe_mk {α : Type u_1} [TopologicalSpace α] (s : Compacts α) (h : (interior s.carrier).Nonempty) :
                                                { toCompacts := s, interior_nonempty' := h } = s
                                                @[simp]
                                                theorem TopologicalSpace.PositiveCompacts.coe_sup {α : Type u_1} [TopologicalSpace α] (s t : PositiveCompacts α) :
                                                (st) = s t
                                                def TopologicalSpace.PositiveCompacts.map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : αβ) (hf : Continuous f) (hf' : IsOpenMap f) (K : PositiveCompacts α) :

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

                                                Equations
                                                  Instances For
                                                    @[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 : PositiveCompacts α) :
                                                    (PositiveCompacts.map f hf hf' s) = f '' s
                                                    theorem TopologicalSpace.PositiveCompacts.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 : PositiveCompacts α) :
                                                    theorem exists_positiveCompacts_subset {α : Type u_1} [TopologicalSpace α] [LocallyCompactSpace α] {U : Set α} (ho : IsOpen U) (hn : U.Nonempty) :

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

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

                                                    Equations
                                                      Instances For
                                                        @[simp]
                                                        theorem TopologicalSpace.PositiveCompacts.coe_prod {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (K : PositiveCompacts α) (L : PositiveCompacts β) :
                                                        (K.prod L) = K ×ˢ L

                                                        Compact open sets #

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

                                                        Instances For

                                                          See Note [custom simps projection].

                                                          Equations
                                                            Instances For

                                                              Reinterpret a compact open as an open.

                                                              Equations
                                                                Instances For

                                                                  Reinterpret a compact open as a clopen.

                                                                  Equations
                                                                    Instances For
                                                                      theorem TopologicalSpace.CompactOpens.ext {α : Type u_1} [TopologicalSpace α] {s t : CompactOpens α} (h : s = t) :
                                                                      s = t
                                                                      theorem TopologicalSpace.CompactOpens.ext_iff {α : Type u_1} [TopologicalSpace α] {s t : CompactOpens α} :
                                                                      s = t s = t
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_mk {α : Type u_1} [TopologicalSpace α] (s : Compacts α) (h : IsOpen s.carrier) :
                                                                      { toCompacts := s, isOpen' := h } = s
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_sup {α : Type u_1} [TopologicalSpace α] (s t : CompactOpens α) :
                                                                      (st) = s t
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_finsetSup {α : Type u_1} [TopologicalSpace α] {ι : Type u_4} {f : ιCompactOpens α} {s : Finset ι} :
                                                                      (s.sup f) = is, (f i)
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_inf {α : Type u_1} [TopologicalSpace α] [QuasiSeparatedSpace α] (s t : CompactOpens α) :
                                                                      (st) = s t
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_sdiff {α : Type u_1} [TopologicalSpace α] [T2Space α] (s t : CompactOpens α) :
                                                                      ↑(s \ t) = s \ t
                                                                      @[simp]
                                                                      @[simp]
                                                                      theorem TopologicalSpace.CompactOpens.coe_himp {α : Type u_1} [TopologicalSpace α] [CompactSpace α] [T2Space α] (s t : CompactOpens α) :
                                                                      ↑(s t) = s t
                                                                      def TopologicalSpace.CompactOpens.map {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (f : αβ) (hf : Continuous f) (hf' : IsOpenMap f) (s : CompactOpens α) :

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

                                                                      Equations
                                                                        Instances For
                                                                          @[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 : CompactOpens α) :
                                                                          (map f hf hf' s).toCompacts = Compacts.map f hf s.toCompacts
                                                                          @[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 : CompactOpens α) :
                                                                          (map f hf hf' s) = f '' s
                                                                          @[simp]
                                                                          theorem TopologicalSpace.CompactOpens.map_id {α : Type u_1} [TopologicalSpace α] (K : CompactOpens α) :
                                                                          map id K = K
                                                                          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 : CompactOpens α) :
                                                                          map (f g) K = map f hf hf' (map g hg hg' K)

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

                                                                          Equations
                                                                            Instances For
                                                                              @[simp]
                                                                              theorem TopologicalSpace.CompactOpens.coe_prod {α : Type u_1} {β : Type u_2} [TopologicalSpace α] [TopologicalSpace β] (K : CompactOpens α) (L : CompactOpens β) :
                                                                              (K.prod L) = K ×ˢ L