Signs in constructions on homological complexes
In this file, we shall introduce various typeclasses which will allow the construction of the total complex of a bicomplex and of the the monoidal category structure on categories of homological complexes (TODO).
The most important definition is that of TotalComplexShape c₁ c₂ c₁₂ given
three complex shapes c₁, c₂, c₁₂: it allows the definition of a total
complex functor HomologicalComplex₂ C c₁ c₂ ⥤ HomologicalComplex C c₁₂ (at least
when suitable coproducts exist).
In particular, we construct an instance of TotalComplexShape c c c when c : ComplexShape I
and I is an additive monoid equipped with a group homomorphism ε' : Multiplicative I → ℤˣ
satisfying certain properties (see ComplexShape.TensorSigns).
A total complex shape for three complexes shapes c₁, c₂, c₁₂ on three types
I₁, I₂ and I₁₂ consists of the data and properties that will allow the construction
of a total complex functor HomologicalComplex₂ C c₁ c₂ ⥤ HomologicalComplex C c₁₂ which
sends K to a complex which in degree i₁₂ : I₁₂ consists of the coproduct
of the (K.X i₁).X i₂ such that π ⟨i₁, i₂⟩ = i₁₂.
- π : I₁ × I₂ → I₁₂
a map on indices
the sign of the horizontal differential in the total complex
the sign of the vertical differential in the total complex
Instances
The map I₁ × I₂ → I₁₂ on indices given by TotalComplexShape c₁ c₂ c₁₂.
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The sign of the horizontal differential in the total complex.
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The sign of the vertical differential in the total complex.
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If I is an additive monoid and c : ComplexShape I, c.TensorSigns contains the data of
map ε : I → ℤˣ and properties which allows the construction of a TotalComplexShape c c c.
the signs which appear in the vertical differential of the total complex
Instances
The signs which appear in the vertical differential of the total complex.
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When we have six complex shapes c₁, c₂, c₃, c₁₂, c₂₃, c, and total functors
HomologicalComplex₂ C c₁ c₂ ⥤ HomologicalComplex C c₁₂,
HomologicalComplex₂ C c₁₂ c₃ ⥤ HomologicalComplex C c,
HomologicalComplex₂ C c₂ c₃ ⥤ HomologicalComplex C c₂₃,
HomologicalComplex₂ C c₁ c₂₂₃ ⥤ HomologicalComplex C c, we get two ways to
compute the total complex of a triple complex in HomologicalComplex₃ C c₁ c₂ c₃, then
under this assumption [Associative c₁ c₂ c₃ c₁₂ c₂₃ c], these two complexes
canonically identify (without introducing signs).
Instances
The map I₁ × I₂ × I₃ → j that is obtained using TotalComplexShape c₁ c₂ c₁₂
and TotalComplexShape c₁₂ c₃ c when c₁ : ComplexShape I₁, c₂ : ComplexShape I₂,
c₃ : ComplexShape I₃, c₁₂ : ComplexShape I₁₂ and c : ComplexShape J.
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The GradedObject.BifunctorComp₁₂IndexData which arises from complex shapes.
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The GradedObject.BifunctorComp₂₃IndexData which arises from complex shapes.
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A total complex shape symmetry contains the data and properties which allow the
identification of the two total complex functors
HomologicalComplex₂ C c₁ c₂ ⥤ HomologicalComplex C c₁₂
and HomologicalComplex₂ C c₂ c₁ ⥤ HomologicalComplex C c₁₂ via the flip.
the signs involved in the symmetry isomorphism of the total complex
Instances
The signs involved in the symmetry isomorphism of the total complex.
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The symmetry bijection (π c₂ c₁ c₁₂ ⁻¹' {j}) ≃ (π c₁ c₂ c₁₂ ⁻¹' {j}).
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The obvious TotalComplexShapeSymmetry c₂ c₁ c₁₂ deduced from a
TotalComplexShapeSymmetry c₁ c₂ c₁₂.
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This typeclass expresses that the signs given by [TotalComplexShapeSymmetry c₁ c₂ c₁₂]
and by [TotalComplexShapeSymmetry c₂ c₁ c₁₂] are compatible.