The graded splitting algebra carrier #
The full splitting algebra is the sum over the integer degrees of
the graded components: degree a is the line through the
starting bidegree ((−a)⁺, a⁺), so nonnegative degrees extend
the M-arity and negative degrees the M'-arity. The balanced
degree is the algebra of the splitting chain, carrying the unit.
The graded component at an integer degree: the line
through ((−a)⁺, a⁺) — nonnegative degrees raise the M-arity,
negative degrees the M'-arity.
Equations
- RS.chainBGrComponent A M M' d a = RS.chainBdeg A M M' d (-a).toNat a.toNat
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The degree-zero component is the splitting-chain algebra.
Equations
- RS.chainBGrComponentZeroIso A M M' d = RS.chainBdegZeroIso A M M' d
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The iterated line shift: raising both offsets n times is
the identity on the colimit.
Equations
- RS.chainBdegShiftIso A M M' d p₀ q₀ 0 = CategoryTheory.Iso.refl (RS.chainBdeg A M M' d (p₀ + 0) (q₀ + 0))
- RS.chainBdegShiftIso A M M' d p₀ q₀ n.succ = RS.chainBdegSuccIso A M M' d (p₀ + n) (q₀ + n) ≪≫ RS.chainBdegShiftIso A M M' d p₀ q₀ n
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The pairwise offsets normalise to the sum degree: the line through the sum of two components' offsets is the raised line of the sum-degree component.
Equations
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The pairwise graded product: two components multiply into the sum-degree component through the offset normalisation.
Equations
- RS.chainBGrCompMul A M M' d a b = CategoryTheory.CategoryStruct.comp (RS.chainBdegMul A M M' d (-a).toNat a.toNat (-b).toNat b.toNat) (RS.chainBGrCompNormIso A M M' d a b).hom
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The graded splitting algebra carrier: the sum of the graded components over all integer degrees.
Equations
- RS.chainBGr A M M' d = ∐ fun (a : ℤ) => RS.chainBGrComponent A M M' d a
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The inclusion of a graded component.
Equations
- RS.chainBGrι A M M' d a = CategoryTheory.Limits.Sigma.ι (fun (a : ℤ) => RS.chainBGrComponent A M M' d a) a
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The unit of the graded splitting algebra: the unit of the balanced algebra, in degree zero.
Equations
- RS.chainBGrUnit A M M' d = CategoryTheory.CategoryStruct.comp (RS.chainBUnit A M M' d) (CategoryTheory.CategoryStruct.comp (RS.chainBGrComponentZeroIso A M M' d).inv (RS.chainBGrι A M M' d 0))
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The projection onto the degree-zero component: the identity in degree zero and zero elsewhere.
Equations
- RS.chainBGrProjZero A M M' d = CategoryTheory.Limits.Sigma.desc fun (b : ℤ) => if h : b = 0 then CategoryTheory.eqToHom ⋯ else 0
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The degree-zero inclusion is split by the projection.
The degree-zero inclusion is split by the projection.
The graded unit does not vanish when the balanced unit does not: the degree-zero retraction detects it.
The multiply-then-include maps against a fixed left component form a cocone over the right degree.
Equations
- One or more equations did not get rendered due to their size.
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The left-component stage of the graded multiplication: a fixed component multiplies the whole carrier degreewise.
Equations
- One or more equations did not get rendered due to their size.
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On a right component, the stage multiplication is the pairwise product followed by the sum-degree inclusion.
On a right component, the stage multiplication is the pairwise product followed by the sum-degree inclusion.
The stage multiplications form a cocone over the left degree.
Equations
- RS.chainBGrMulCocone A M M' d = { pt := RS.chainBGr A M M' d, ι := CategoryTheory.Discrete.natTrans fun (a : CategoryTheory.Discrete ℤ) => RS.chainBGrMulStage A M M' d a.as }
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The multiplication of the graded splitting algebra: the pairwise graded products assembled over both degrees.
Equations
- One or more equations did not get rendered due to their size.
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On a left component, the multiplication is the stage multiplication.
On a left component, the multiplication is the stage multiplication.
Defining equation of the graded multiplication: on a pair of components it is the pairwise product followed by the sum-degree inclusion.
Defining equation of the graded multiplication: on a pair of components it is the pairwise product followed by the sum-degree inclusion.
Under the degree-zero identification, the stage insertions of the balanced line are the stage transports followed by the stage inclusions of the splitting-chain algebra.
Under the degree-zero identification, the stage insertions of the balanced line are the stage transports followed by the stage inclusions of the splitting-chain algebra.
The iterated shift commutes with the offset transports.
Degree transports on a component are offset transports.
Line transports along paired offset equalities are offset transports.
The normaliser decomposes as an offset transport followed by the iterated shift.
The offset normalisation is braiding-compatible: the normaliser of the swapped degrees followed by the sum-degree transport is the offset transport followed by the normaliser.
Commutativity of the pairwise graded product: the braiding followed by the swapped product is the product, up to the sum-degree transport.
Degree transports are absorbed by the inclusions.
Maps out of the carrier tensored on the right are determined by their restrictions to the components.
Maps out of the carrier tensored on the left are determined by their restrictions to the components.
Maps out of a tensor square of the carrier agree once they agree on all pairs of components.
The graded multiplication is commutative: the braiding followed by the multiplication is the multiplication.
The stage-level seed law on the left #
The left unit law of the seed at two indices: multiplying by the seed on the left is the transition, through the unit braiding.
Stage computation of the shift and the normalisation #
The iterated shift peels off one raise at a time.
Under the tail identification, the stage insertions of the raised line are the stage transports followed by the next stage insertions of the line.
Under the tail identification, the stage insertions of the raised line are the stage transports followed by the next stage insertions of the line.
Under the iterated shift, the stage insertions of the raised line are the stage transports followed by the shifted stage insertions of the line.
Under the offset normalisation, the stage insertions of the summed line are the stage transports followed by the shifted stage insertions of the sum-degree component.
Under the offset normalisation, the stage insertions of the summed line are the stage transports followed by the shifted stage insertions of the sum-degree component.
Tensor surgery #
Component insertions #
The stage insertion of a graded component.
Equations
- RS.chainBGrCompι A M M' d a k = RS.chainBdegι A M M' d (-a).toNat a.toNat k
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Stage transports along a stage equality are absorbed by the component insertions.
The component insertions absorb the transitions.
Degree transports intertwine the component insertions with the stage transports.
Stage computation and associativity of the pairwise #
product
Maps out of a component tensored on the left are determined by the stages.
Maps out of a triple tensor of components agree once they agree on all triples of stages.
Defining equation of the pairwise graded product on stages: the two-index stage multiplication, transported and inserted at the shifted stage of the sum-degree component.
Defining equation of the pairwise graded product on stages: the two-index stage multiplication, transported and inserted at the shifted stage of the sum-degree component.
Associativity of the pairwise graded product: the two bracketings of a triple product agree up to the sum-degree transport reassociating the degrees.
Associativity of the graded multiplication #
Sandwich extensionality: maps out of a tensor product with the carrier in the middle slot are determined by the components there.
Maps out of a tensor square of the carrier whiskered on the right agree once they agree on all pairs of components.
Maps out of a triple tensor of the carrier agree once they agree on all triples of components.
Associativity of the graded multiplication: the two bracketings of a triple product agree.
The unit laws #
The unit lands at the bottom stage: through the degree-zero identification, the unit of the balanced algebra is the seed at the bottom stage of the degree-zero component.
The stage rule of the pairwise product at degree zero on the left, with the balanced-line arities normalised.
The left unit law of the pairwise graded product: the included unit against a component multiplies as the left unitor, through the sum-degree transport.
The left unit law of the pairwise graded product: the included unit against a component multiplies as the left unitor, through the sum-degree transport.
The left unit law of the graded splitting algebra: the unit against the carrier is the left unitor.
The right unit law of the graded splitting algebra: the carrier against the unit is the right unitor.
The monoid object #
The graded splitting algebra is a monoid object: the degree-zero unit and the graded multiplication satisfy the monoid laws.
Equations
- RS.chainBGrMonObj A M M' d = { one := RS.chainBGrUnit A M M' d, mul := RS.chainBGrMul A M M' d, one_mul := ⋯, mul_one := ⋯, mul_assoc := ⋯ }
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The graded splitting algebra is commutative.