The category of groups in a Cartesian monoidal category #
We define group objects in Cartesian monoidal categories.
We show that the associativity diagram of a group object is always Cartesian and deduce that morphisms of group objects commute with taking inverses.
We show that a finite-product-preserving functor takes group objects to group objects.
An additive group object internal to a cartesian monoidal category.
Also see the bundled AddGrp.
The negation in a group object
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A group object internal to a cartesian monoidal category. Also see the bundled Grp.
The inverse in a group object
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The inverse in a group object
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- CategoryTheory.MonObj.termι = Lean.ParserDescr.node `CategoryTheory.MonObj.termι 1024 (Lean.ParserDescr.symbol "ι")
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The inverse in a group object
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An additive group object in a Cartesian monoidal category.
- X : C
The underlying object in the ambient monoidal category
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A group object in a Cartesian monoidal category.
- X : C
The underlying object in the ambient monoidal category
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Alias of CategoryTheory.Grp.
A group object in a Cartesian monoidal category.
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A group object is a monoid object.
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An additive group object is an additive monoid object.
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The trivial group object.
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The trivial additive group object.
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- CategoryTheory.Grp.instInhabited = { default := CategoryTheory.Grp.trivial C }
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- CategoryTheory.AddGrp.instInhabited = { default := CategoryTheory.AddGrp.trivial C }
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Alias of CategoryTheory.Grp.id_hom_hom.
Alias of CategoryTheory.Grp.comp_hom_hom.
Constructor for morphisms in Grp C.
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- CategoryTheory.Grp.homMk' f = { hom := f }
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Constructor for morphisms in AddGrp C.
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- CategoryTheory.AddGrp.homMk' f = { hom := f }
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Construct a morphism A ⟶ B of Grp C from a map f : A.X ⟶ A.X and a IsMonHom f
instance.
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- CategoryTheory.Grp.homMk f = CategoryTheory.Grp.homMk' { hom := f, isMonHom_hom := inst✝ }
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Construct a morphism A ⟶ B of AddGrp C from a map f : A.X ⟶ A.X and a IsAddMonHom f
instance.
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- CategoryTheory.AddGrp.homMk f = CategoryTheory.AddGrp.homMk' { hom := f, isAddMonHom_hom := inst✝ }
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Construct a morphism Grp.mk G ⟶ Grp.mk H from a map f : G ⟶ H and a IsMonHom f
instance.
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Construct a morphism AddGrp.mk G ⟶ AddGrp.mk H from a map f : G ⟶ H and a IsAddMonHom f
instance.
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Constructor for morphisms in Grp C.
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- CategoryTheory.Grp.homMk'' f one_f mul_f = CategoryTheory.Grp.homMk f
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Constructor for morphisms in AddGrp C.
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- CategoryTheory.AddGrp.homMk'' f one_f mul_f = CategoryTheory.AddGrp.homMk f
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Transfer AddGrpObj along an isomorphism.
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Transfer GrpObj along an isomorphism.
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For inv ≫ inv = 𝟙 see inv_comp_inv.
For neg ≫ neg = 𝟙 see neg_comp_neg.
The map (· * f).
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The map (· + f).
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The associativity diagram of a group object is Cartesian.
In fact, any monoid object whose associativity diagram is Cartesian can be made into a group object (we do not prove this in this file), so we should expect that many properties of group objects follow from this result.
Morphisms of group objects preserve inverses.
Morphisms of group objects preserve negations.
Morphisms of group objects preserve inverses.
A monoid object with invertible homs is a group object.
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The forgetful functor from group objects to monoid objects.
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The forgetful functor from additive group objects to additive monoid objects.
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The forgetful functor from group objects to monoid objects is fully faithful.
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The forgetful functor from additive group objects to additive monoid objects is fully faithful.
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The forgetful functor from group objects to the ambient category.
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The forgetful functor from additive group objects to the ambient category.
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Construct an isomorphism of group objects by giving a monoid isomorphism between the underlying objects.
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Construct an isomorphism of additive group objects by giving an additive monoid isomorphism between the underlying objects.
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Construct an isomorphism of group objects by giving an isomorphism between the underlying objects and checking compatibility with unit and multiplication only in the forward direction.
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- CategoryTheory.Grp.mkIso e one_f mul_f = CategoryTheory.Grp.mkIso' e
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Construct an isomorphism of additive group objects by giving an isomorphism between the underlying objects and checking compatibility with zero and addition only in the forward direction.
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- CategoryTheory.AddGrp.mkIso e one_f mul_f = CategoryTheory.AddGrp.mkIso' e
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Alias of CategoryTheory.Grp.mkIso_hom_hom_hom.
Alias of CategoryTheory.Grp.mkIso_inv_hom_hom.
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- A.uniqueHomFromTrivial = (have this := CategoryTheory.InducedCategory.homEquiv; this).unique
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- A.uniqueHomFromTrivial = (have this := CategoryTheory.InducedCategory.homEquiv; this).unique
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- A.uniqueHomToTrivial = (have this := CategoryTheory.InducedCategory.homEquiv; this).unique
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- A.uniqueHomToTrivial = (have this := CategoryTheory.InducedCategory.homEquiv; this).unique
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Alias of CategoryTheory.Grp.whiskerLeft_hom_hom.
Alias of CategoryTheory.Grp.whiskerRight_hom_hom.
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Alias of CategoryTheory.Grp.fst_hom_hom.
Alias of CategoryTheory.Grp.snd_hom_hom.
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Alias of CategoryTheory.Grp.braiding_hom_hom_hom.
Alias of CategoryTheory.Grp.braiding_inv_hom_hom.
The image of a group object under a monoidal functor is a group object.
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- CategoryTheory.Functor.grpObjObj = { toMonObj := CategoryTheory.Functor.monObjObj G, inv := F.map CategoryTheory.GrpObj.inv, left_inv := ⋯, right_inv := ⋯ }
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The image of an additive group object under a monoidal functor is an additive group object.
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- CategoryTheory.Functor.addGrpObjObj = { toAddMonObj := CategoryTheory.Functor.addMonObjObj G, neg := F.map CategoryTheory.AddGrpObj.neg, left_neg := ⋯, right_neg := ⋯ }
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A finite-product-preserving functor takes group objects to group objects.
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A finite-product-preserving functor takes additive group objects to additive group objects.
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If F : C ⥤ D is a fully faithful monoidal functor, then
F.mapGrp : Grp C ⥤ Grp D is fully faithful too.
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If F : C ⥤ D is a fully faithful monoidal functor, then
F.mapAddGrp : AddGrp C ⥤ AddGrp D is fully faithful too.
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The identity functor is also the identity on group objects.
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The identity functor is also the identity on additive group objects.
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The composition functor is also the composition on group objects.
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The composition functor is also the composition on additive group objects.
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Natural transformations between functors lift to group objects.
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Natural transformations between functors lift to additive group objects.
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Natural isomorphisms between functors lift to group objects.
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- CategoryTheory.Functor.mapGrpNatIso e = CategoryTheory.NatIso.ofComponents (fun (X : CategoryTheory.Grp C) => CategoryTheory.Grp.mkIso (e.app X.X) ⋯ ⋯) ⋯
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Natural isomorphisms between functors lift to additive group objects.
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- CategoryTheory.Functor.mapAddGrpNatIso e = CategoryTheory.NatIso.ofComponents (fun (X : CategoryTheory.AddGrp C) => CategoryTheory.AddGrp.mkIso (e.app X.X) ⋯ ⋯) ⋯
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mapGrp is functorial in the left-exact functor.
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mapAddGrp is functorial in the left-exact functor.
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Pullback a group object along a fully faithful monoidal functor.
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Pullback an additive group object along a fully faithful monoidal functor.
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The essential image of a full and faithful functor between cartesian-monoidal categories is the same on group objects as on objects.
The essential image of a full and faithful functor between cartesian-monoidal categories is the same on additive group objects as on objects.
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- CategoryTheory.Functor.mapGrp.instBraided F = { toMonoidal := CategoryTheory.Functor.mapGrp.instMonoidal F, braided := ⋯ }
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- CategoryTheory.Functor.mapAddGrp.instBraided F = { toMonoidal := CategoryTheory.Functor.mapAddGrp.instMonoidal F, braided := ⋯ }
An adjunction of monoidal functors lifts to an adjunction of their lifts to group objects.
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An adjunction of monoidal functors lifts to an adjunction of their lifts to additive group objects.
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An equivalence of categories lifts to an equivalence of their group objects.
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An equivalence of categories lifts to an equivalence of their additive group objects.
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