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
.
- obj : C
The underlying object of a differential object.
- d : self.obj ⟶ (CategoryTheory.shiftFunctor C 1).obj self.obj
The differential of a differential object.
- d_squared : CategoryTheory.CategoryStruct.comp self.d ((CategoryTheory.shiftFunctor C 1).map self.d) = 0
The differential
d
satisfies thatd² = 0
.
Instances For
A morphism of differential objects is a morphism commuting with the differentials.
- f : X.obj ⟶ Y.obj
The morphism between underlying objects of the two differentiable objects.
- comm : CategoryTheory.CategoryStruct.comp X.d ((CategoryTheory.shiftFunctor C 1).map self.f) = CategoryTheory.CategoryStruct.comp self.f Y.d
Instances For
The identity morphism of a differential object.
Equations
- CategoryTheory.DifferentialObject.Hom.id X = { f := CategoryTheory.CategoryStruct.id X.obj, comm := ⋯ }
Instances For
The composition of morphisms of differential objects.
Equations
- f.comp g = { f := CategoryTheory.CategoryStruct.comp f.f g.f, comm := ⋯ }
Instances For
Equations
- CategoryTheory.DifferentialObject.categoryOfDifferentialObjects = CategoryTheory.Category.mk ⋯ ⋯ ⋯
The forgetful functor taking a differential object to its underlying object.
Equations
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Instances For
Equations
- CategoryTheory.DifferentialObject.instZeroHom = { zero := { f := 0, comm := ⋯ } }
Equations
- CategoryTheory.DifferentialObject.hasZeroMorphisms = CategoryTheory.Limits.HasZeroMorphisms.mk ⋯ ⋯
An isomorphism of differential objects gives an isomorphism of the underlying objects.
Equations
- CategoryTheory.DifferentialObject.isoApp f = { hom := f.hom.f, inv := f.inv.f, hom_inv_id := ⋯, inv_hom_id := ⋯ }
Instances For
An isomorphism of differential objects can be constructed from an isomorphism of the underlying objects that commutes with the differentials.
Equations
- CategoryTheory.DifferentialObject.mkIso f hf = { hom := { f := f.hom, comm := hf }, inv := { f := f.inv, comm := ⋯ }, hom_inv_id := ⋯, inv_hom_id := ⋯ }
Instances For
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
.
Equations
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Instances For
Equations
- CategoryTheory.DifferentialObject.instHasForget₂ S C = { forget₂ := CategoryTheory.DifferentialObject.forget S C, forget_comp := ⋯ }
The category of differential objects itself has a shift functor.
The shift functor on DifferentialObject S C
.
Equations
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Instances For
The shift functor on DifferentialObject S C
is additive.
Equations
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Instances For
The shift by zero is naturally isomorphic to the identity.
Equations
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Instances For
Equations
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