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Mathlib.CategoryTheory.DifferentialObject

Differential objects in a category. #

A differential object in a category with zero morphisms and a shift is an object X equipped with a morphism d : obj ⟶ obj⟦1⟧, such that d^2 = 0.

We build the category of differential objects, and some basic constructions such as the forgetful functor, zero morphisms and zero objects, and the shift functor on differential objects.

A differential object in a category with zero morphisms and a shift is an object obj equipped with a morphism d : obj ⟶ obj⟦1⟧, such that d^2 = 0.

A morphism of differential objects is a morphism commuting with the differentials.

theorem CategoryTheory.DifferentialObject.Hom.ext_iff {S : Type u_1} {inst✝ : AddMonoidWithOne S} {C : Type u} {inst✝¹ : Category.{v, u} C} {inst✝² : Limits.HasZeroMorphisms C} {inst✝³ : HasShift C S} {X Y : DifferentialObject S C} {x y : X.Hom Y} :
x = y x.f = y.f
theorem CategoryTheory.DifferentialObject.Hom.ext {S : Type u_1} {inst✝ : AddMonoidWithOne S} {C : Type u} {inst✝¹ : Category.{v, u} C} {inst✝² : Limits.HasZeroMorphisms C} {inst✝³ : HasShift C S} {X Y : DifferentialObject S C} {x y : X.Hom Y} (f : x.f = y.f) :
x = y

The identity morphism of a differential object.

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The composition of morphisms of differential objects.

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theorem CategoryTheory.DifferentialObject.ext {S : Type u_1} [AddMonoidWithOne S] {C : Type u} [Category.{v, u} C] [Limits.HasZeroMorphisms C] [HasShift C S] {A B : DifferentialObject S C} {f g : A B} (w : f.f = g.f := by aesop_cat) :
f = g

The forgetful functor taking a differential object to its underlying object.

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An isomorphism of differential objects gives an isomorphism of the underlying objects.

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An isomorphism of differential objects can be constructed from an isomorphism of the underlying objects that commutes with the differentials.

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A functor F : C ⥤ D which commutes with shift functors on C and D and preserves zero morphisms can be lifted to a functor DifferentialObject S C ⥤ DifferentialObject S D.

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@[simp]
theorem CategoryTheory.Functor.mapDifferentialObject_map_f {S : Type u_1} [AddMonoidWithOne S] {C : Type u} [Category.{v, u} C] [Limits.HasZeroMorphisms C] [HasShift C S] (D : Type u') [Category.{v', u'} D] [Limits.HasZeroMorphisms D] [HasShift D S] (F : Functor C D) (η : (shiftFunctor C 1).comp F F.comp (shiftFunctor D 1)) (hF : ∀ (c c' : C), F.map 0 = 0) {X✝ Y✝ : DifferentialObject S C} (f : X✝ Y✝) :
((mapDifferentialObject D F η hF).map f).f = F.map f.f
@[simp]
theorem CategoryTheory.Functor.mapDifferentialObject_obj_d {S : Type u_1} [AddMonoidWithOne S] {C : Type u} [Category.{v, u} C] [Limits.HasZeroMorphisms C] [HasShift C S] (D : Type u') [Category.{v', u'} D] [Limits.HasZeroMorphisms D] [HasShift D S] (F : Functor C D) (η : (shiftFunctor C 1).comp F F.comp (shiftFunctor D 1)) (hF : ∀ (c c' : C), F.map 0 = 0) (X : DifferentialObject S C) :
((mapDifferentialObject D F η hF).obj X).d = CategoryStruct.comp (F.map X.d) (η.app X.obj)
@[simp]
theorem CategoryTheory.Functor.mapDifferentialObject_obj_obj {S : Type u_1} [AddMonoidWithOne S] {C : Type u} [Category.{v, u} C] [Limits.HasZeroMorphisms C] [HasShift C S] (D : Type u') [Category.{v', u'} D] [Limits.HasZeroMorphisms D] [HasShift D S] (F : Functor C D) (η : (shiftFunctor C 1).comp F F.comp (shiftFunctor D 1)) (hF : ∀ (c c' : C), F.map 0 = 0) (X : DifferentialObject S C) :
((mapDifferentialObject D F η hF).obj X).obj = F.obj X.obj
@[reducible, inline]
abbrev CategoryTheory.DifferentialObject.HomSubtype (S : Type u_1) [AddMonoidWithOne S] (C : Type (u + 1)) [LargeCategory C] [Limits.HasZeroMorphisms C] {FC : CCType u_2} {CC : CType u_3} [(X Y : C) → FunLike (FC X Y) (CC X) (CC Y)] [ConcreteCategory C FC] [HasShift C S] (X Y : DifferentialObject S C) :
Type u_2

The type of C-morphisms that can be lifted back to morphisms in the category DifferentialObject.

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instance CategoryTheory.DifferentialObject.instFunLikeHomSubtypeObj (S : Type u_1) [AddMonoidWithOne S] (C : Type (u + 1)) [LargeCategory C] [Limits.HasZeroMorphisms C] {FC : CCType u_2} {CC : CType u_3} [(X Y : C) → FunLike (FC X Y) (CC X) (CC Y)] [ConcreteCategory C FC] [HasShift C S] (X Y : DifferentialObject S C) :
FunLike (HomSubtype S C X Y) (CC X.obj) (CC Y.obj)
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instance CategoryTheory.DifferentialObject.concreteCategoryOfDifferentialObjects (S : Type u_1) [AddMonoidWithOne S] (C : Type (u + 1)) [LargeCategory C] [Limits.HasZeroMorphisms C] {FC : CCType u_2} {CC : CType u_3} [(X Y : C) → FunLike (FC X Y) (CC X) (CC Y)] [ConcreteCategory C FC] [HasShift C S] :
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The category of differential objects itself has a shift functor.

The shift functor on DifferentialObject S C.

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The shift functor on DifferentialObject S C is additive.

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The shift by zero is naturally isomorphic to the identity.

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