Documentation

Mathlib.GroupTheory.Subgroup.Center

Centers of subgroups #

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def Subgroup.center (G : Type u_1) [Group G] :
Subgroup G

The center of a group G is the set of elements that commute with everything in G

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    def AddSubgroup.center (G : Type u_1) [AddGroup G] :
    AddSubgroup G

    The center of an additive group G is the set of elements that commute with everything in G

    Instances For
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      theorem Subgroup.coe_center (G : Type u_1) [Group G] :
      ↑(center G) = Set.center G
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      theorem AddSubgroup.coe_center (G : Type u_1) [AddGroup G] :
      ↑(center G) = Set.addCenter G
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      @[simp]
      theorem Subgroup.center_toSubmonoid (G : Type u_1) [Group G] :
      (center G).toSubmonoid = Submonoid.center G
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      @[simp]
      theorem AddSubgroup.center_toAddSubmonoid (G : Type u_1) [AddGroup G] :
      (center G).toAddSubmonoid = AddSubmonoid.center G
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      instance Subgroup.center.isMulCommutative (G : Type u_1) [Group G] :
      IsMulCommutative ↥(center G)
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      def Subgroup.centerCongr {G : Type u_1} [Group G] {H : Type u_2} [Group H] (e : G ≃* H) :
      ↥(center G) ≃* ↥(center H)

      The center of isomorphic groups are isomorphic.

      Instances For
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        def AddSubgroup.centerCongr {G : Type u_1} [AddGroup G] {H : Type u_2} [AddGroup H] (e : G ≃+ H) :
        ↥(center G) ≃+ ↥(center H)

        The center of isomorphic additive groups are isomorphic.

        Instances For
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          @[simp]
          theorem AddSubgroup.centerCongr_symm_apply_coe {G : Type u_1} [AddGroup G] {H : Type u_2} [AddGroup H] (e : G ≃+ H) (s : ↥(AddSubsemigroup.center H)) :
          ↑((centerCongr e).symm s) = e.symm ↑s
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          @[simp]
          theorem AddSubgroup.centerCongr_apply_coe {G : Type u_1} [AddGroup G] {H : Type u_2} [AddGroup H] (e : G ≃+ H) (r : ↥(AddSubsemigroup.center G)) :
          ↑((centerCongr e) r) = e ↑r
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          @[simp]
          theorem Subgroup.centerCongr_apply_coe {G : Type u_1} [Group G] {H : Type u_2} [Group H] (e : G ≃* H) (r : ↥(Subsemigroup.center G)) :
          ↑((centerCongr e) r) = e ↑r
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          @[simp]
          theorem Subgroup.centerCongr_symm_apply_coe {G : Type u_1} [Group G] {H : Type u_2} [Group H] (e : G ≃* H) (s : ↥(Subsemigroup.center H)) :
          ↑((centerCongr e).symm s) = e.symm ↑s
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          def Subgroup.centerToMulOpposite (G : Type u_1) [Group G] :
          ↥(center G) ≃* ↥(center Gᵐᵒᵖ)

          The center of a group is isomorphic to the center of its opposite.

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            def AddSubgroup.centerToAddOpposite (G : Type u_1) [AddGroup G] :
            ↥(center G) ≃+ ↥(center Gᵃᵒᵖ)

            The center of an additive group is isomorphic to the center of its opposite.

            Instances For
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              @[simp]
              theorem AddSubgroup.centerToAddOpposite_symm_apply_coe (G : Type u_1) [AddGroup G] (r : ↥(AddSubsemigroup.center Gᵃᵒᵖ)) :
              ↑((centerToAddOpposite G).symm r) = AddOpposite.unop ↑r
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              @[simp]
              theorem Subgroup.centerToMulOpposite_apply_coe (G : Type u_1) [Group G] (r : ↥(Subsemigroup.center G)) :
              ↑((centerToMulOpposite G) r) = MulOpposite.op ↑r
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              @[simp]
              theorem Subgroup.centerToMulOpposite_symm_apply_coe (G : Type u_1) [Group G] (r : ↥(Subsemigroup.center Gᵐᵒᵖ)) :
              ↑((centerToMulOpposite G).symm r) = MulOpposite.unop ↑r
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              @[simp]
              theorem AddSubgroup.centerToAddOpposite_apply_coe (G : Type u_1) [AddGroup G] (r : ↥(AddSubsemigroup.center G)) :
              ↑((centerToAddOpposite G) r) = AddOpposite.op ↑r
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              theorem Subgroup.mem_center_iff {G : Type u_1} [Group G] {z : G} :
              z ∈ center G ↔ ∀ (g : G), g * z = z * g
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              theorem AddSubgroup.mem_center_iff {G : Type u_1} [AddGroup G] {z : G} :
              z ∈ center G ↔ ∀ (g : G), g + z = z + g
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              @[implicit_reducible]
              instance Subgroup.decidableMemCenter {G : Type u_1} [Group G] (z : G) [Decidable (∀ (g : G), g * z = z * g)] :
              Decidable (z ∈ center G)
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              instance Subgroup.centerCharacteristic {G : Type u_1} [Group G] :
              (center G).Characteristic
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              instance AddSubgroup.centerCharacteristic {G : Type u_1} [AddGroup G] :
              (center G).Characteristic
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              theorem CommGroup.center_eq_top {G : Type u_2} [CommGroup G] :
              Subgroup.center G = ⊤
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              @[implicit_reducible]
              def Group.commGroupOfCenterEqTop {G : Type u_1} [Group G] (h : Subgroup.center G = ⊤) :
              CommGroup G

              A group is commutative if the center is the whole group

              Instances For
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                instance Subgroup.instNormalCenter {G : Type u_1} [Group G] :
                (center G).Normal
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                instance AddSubgroup.instNormalCenter {G : Type u_1} [AddGroup G] :
                (center G).Normal
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                theorem Subgroup.center_le_normalizer {G : Type u_1} [Group G] {H : Subgroup G} :
                center G ≤ normalizer ↑H
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                theorem AddSubgroup.center_le_normalizer {G : Type u_1} [AddGroup G] {H : AddSubgroup G} :
                center G ≤ normalizer ↑H
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                theorem IsConj.eq_of_left_mem_center {M : Type u_2} [Monoid M] {g h : M} (H : IsConj g h) (Hg : g ∈ Set.center M) :
                g = h
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                theorem IsConj.eq_of_right_mem_center {M : Type u_2} [Monoid M] {g h : M} (H : IsConj g h) (Hh : h ∈ Set.center M) :
                g = h
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                theorem ConjClasses.mk_bijOn (G : Type u_2) [Group G] :
                Set.BijOn ConjClasses.mk (↑(Subgroup.center G)) (noncenter G)ᶜ