The tensor product of two super modules #
For a super-commutative ℂ-algebra S and two modules M, N over
it (RS.SuperCommAlgebra.Mod) this file builds the tensor product
M ⊗_S N as another S-module, together with the canonical
balanced map into it and its universal property.
The underlying ℤ/2-graded ℂ-space is the graded tensor product of
RS.SuperVect.tensorObj: the even part of M ⊗_ℂ N is
(M₀ ⊗ N₀) × (M₁ ⊗ N₁) and the odd part is (M₀ ⊗ N₁) × (M₁ ⊗ N₀),
where M₀ = M.even and M₁ = M.odd. Balancing over S is
imposed by quotienting each degree by the span of the relators
listed below.
The sign convention #
A left module over a super-commutative algebra is a right module
under m · a = (−1)^{|a||m|} a · m, and the balancing relation of
the tensor product is (m · a) ⊗ n = m ⊗ (a · n). Written with
left actions throughout, the relator at homogeneous a, m, n
is
(a · m) ⊗ n − (−1)^{|a||m|} m ⊗ (a · n),
so the only sign is a −1 when both the scalar and the left
argument are odd; the parity of n never enters. The eight
relator families are relEvenXYZ in total degree
|a| + |m| + |n| = 0 and relOddXYZ in total degree 1, four
each, indexed by the parity pattern (|a|, |m|, |n|).
The S-action on the quotient is the action on the left factor,
with no sign: a · (m ⊗ n) = (a · m) ⊗ n. It descends because
a · ((b · m) ⊗ n − (−1)^{|b||m|} m ⊗ (b · n)) is (−1)^{|a||b|}
times the relator of b at (a · m, n); this is the one place
where the super-commutativity of S is used, and it is the reason
the construction needs a commutative base.
Contents #
RS.SuperCommAlgebra.Mod.actEE_actEE_command its five companions: an even scalar commutes with every scalar, and two odd scalars anticommute, in their action on a module.RS.tensorLeftDiag,RS.tensorLeftSwap: the two shapes of a parity block acting on the left factor of a two-summand graded tensor product, degree-preserving and degree-reversing.RS.descendAct: descent of a bilinear action along a pair of quotients.RS.SuperCommAlgebra.Mod.balEven,balOdd: the balancing submodules, andpreActEE,preActEO,preActOE,preActOO: the four action blocks before quotienting, with the ten module laws proved at that level.RS.SuperCommAlgebra.Mod.tensor: the tensor product as anS-module.RS.SuperCommAlgebra.Mod.tmulEE,tmulEO,tmulOE,tmulOO: the canonical map, with its eight balancing laws and its eight action laws.RS.SuperCommAlgebra.Mod.liftEven,liftOddandliftEven_unique,liftOdd_unique: the universal property, packaged asexists_unique_liftEvenandexists_unique_liftOdd.
Parity blocks acting on the left factor #
A pair of parity blocks acting on the left factor of a two-summand graded tensor product, in the degree-preserving pattern: each summand stays where it is.
Equations
- RS.tensorLeftDiag P Q f g = { toFun := fun (a : A) => (LinearMap.rTensor P (f a)).prodMap (LinearMap.rTensor Q (g a)), map_add' := ⋯, map_smul' := ⋯ }
Instances For
The degree-preserving block pattern, evaluated.
A pair of parity blocks acting on the left factor of a two-summand graded tensor product, in the degree-reversing pattern: the two summands are interchanged.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The degree-reversing block pattern, evaluated.
Descent of an action along a quotient #
Descend a bilinear action along a pair of quotients: a
bilinear action of A carrying a submodule R of its source into
a submodule R' of its target induces an action on the
quotients.
Instances For
The descended action, evaluated on a class.
Commutation of the action blocks #
The graded tensor product over ℂ #
The even component of the graded ℂ-tensor product of the underlying super spaces.
Instances For
The odd component of the graded ℂ-tensor product of the underlying super spaces.
Instances For
The balancing relators #
The even-degree relator at parity pattern odd-even-odd. The
scalar is odd and the left argument even, so the Koszul sign is
+1.
Instances For
The even-degree relator at parity pattern odd-odd-even. Both
the scalar and the left argument are odd, so the Koszul sign is
−1 and the two terms are added.
Instances For
The balancing submodule in even degree: the span of the four even-degree relator families.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The balancing submodule in odd degree: the span of the four odd-degree relator families.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The even-even-even relators are balanced.
The even-odd-odd relators are balanced.
The odd-even-odd relators are balanced.
The odd-odd-even relators are balanced.
The even-even-odd relators are balanced.
The even-odd-even relators are balanced.
The odd-even-even relators are balanced.
The odd-odd-odd relators are balanced.
The four action blocks before quotienting #
The even-even block, evaluated.
The even-odd block, evaluated.
The odd-even block, evaluated.
The odd-odd block, evaluated.
The module laws before quotienting #
The unit acts as the identity on the even part.
The unit acts as the identity on the odd part.
The blocks preserve balancing #
The tensor product #
The tensor product of two super modules over a
super-commutative ℂ-algebra: the graded ℂ-tensor product of the
underlying super spaces, quotiented in each degree by the
balancing relators, with the S-action induced from the action on
the left factor.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The canonical balanced map #
The canonical map, even times even.
Equations
- M.tmulEE N = (TensorProduct.mk ℂ M.even N.even).compr₂ ((M.balEven N).mkQ ∘ₗ LinearMap.inl ℂ (TensorProduct ℂ M.even N.even) (TensorProduct ℂ M.odd N.odd))
Instances For
The canonical map, odd times odd.
Equations
- M.tmulOO N = (TensorProduct.mk ℂ M.odd N.odd).compr₂ ((M.balEven N).mkQ ∘ₗ LinearMap.inr ℂ (TensorProduct ℂ M.even N.even) (TensorProduct ℂ M.odd N.odd))
Instances For
The canonical map, even times odd.
Equations
- M.tmulEO N = (TensorProduct.mk ℂ M.even N.odd).compr₂ ((M.balOdd N).mkQ ∘ₗ LinearMap.inl ℂ (TensorProduct ℂ M.even N.odd) (TensorProduct ℂ M.odd N.even))
Instances For
The canonical map, odd times even.
Equations
- M.tmulOE N = (TensorProduct.mk ℂ M.odd N.even).compr₂ ((M.balOdd N).mkQ ∘ₗ LinearMap.inr ℂ (TensorProduct ℂ M.even N.odd) (TensorProduct ℂ M.odd N.even))
Instances For
The even-even canonical map, evaluated. Not a simp lemma:
the quotient class is the implementation, and tmulEE is the
interface the computation rules downstream are stated in.
The odd-odd canonical map, evaluated. Not a simp lemma, for
the reason given at tmulEE_apply.
The even-odd canonical map, evaluated. Not a simp lemma, for
the reason given at tmulEE_apply.
The odd-even canonical map, evaluated. Not a simp lemma, for
the reason given at tmulEE_apply.
Balancing #
The action on the canonical map #
The universal property #
The even-degree lift: a pair of ℂ-bilinear maps out of the even-even and odd-odd blocks, balanced against the four even-degree relator families, factors through the even part of the tensor product.
Equations
- M.liftEven N fee foo hee hoo hoeo hooe = (M.balEven N).liftQ ((TensorProduct.lift fee).coprod (TensorProduct.lift foo)) ⋯
Instances For
The odd-degree lift: a pair of ℂ-bilinear maps out of the even-odd and odd-even blocks, balanced against the four odd-degree relator families, factors through the odd part of the tensor product.
Equations
- M.liftOdd N feo foe heeo heoe hoee hooo = (M.balOdd N).liftQ ((TensorProduct.lift feo).coprod (TensorProduct.lift foe)) ⋯
Instances For
The even-degree lift computes on even-even products.
The even-degree lift computes on odd-odd products.
The odd-degree lift computes on even-odd products.
The odd-degree lift computes on odd-even products.
Uniqueness in even degree: the even part of the tensor product is generated by the even-even and odd-odd products.
Uniqueness in odd degree: the odd part of the tensor product is generated by the even-odd and odd-even products.
The universal property in even degree: a balanced pair of ℂ-bilinear maps out of the even-even and odd-odd blocks factors uniquely through the even part of the tensor product.
The universal property in odd degree: a balanced pair of ℂ-bilinear maps out of the even-odd and odd-even blocks factors uniquely through the odd part of the tensor product.