Tensor products and linear maps #
This file defines TensorProduct.map, the R-linear map from M ⊗ N to M₂ ⊗ N₂ defined by
a pair of linear (or more generally semilinear) maps f : M → M₂ and g : N → N₂.
The notation f ⊗ₘ g is available for this map.
We also define one-sided versions lTensor and rTensor.
Tags #
bilinear, tensor, tensor product
The tensor product of a pair of linear maps between modules.
Equations
- TensorProduct.map f g = TensorProduct.lift ((TensorProduct.mk R₂ M₂ N₂).compl₂ g ∘ₛₗ f)
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The tensor product of a pair of linear maps between modules.
Equations
- One or more equations did not get rendered due to their size.
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Given semilinear maps f : M → P, g : N → Q, if we identify M ⊗ N with N ⊗ M and P ⊗ Q
with Q ⊗ P, then this lemma states that f ⊗ g = g ⊗ f.
Alias of TensorProduct.range_map_eq_span_tmul.
Given submodules p ⊆ P and q ⊆ Q, this is the natural map: p ⊗ q → P ⊗ Q.
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The tensor product of a pair of semilinear maps between modules, bilinear in both maps.
Equations
- TensorProduct.mapBilinear σ₁₂ M N M₂ N₂ = LinearMap.mk₂ R₂ TensorProduct.map ⋯ ⋯ ⋯ ⋯
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The canonical linear map from M₂ ⊗[R₂] (P →ₛₗ[σ₁₂] N₂) to P →ₛₗ[σ₁₂] M₂ ⊗[R₂] N₂.
Equations
- TensorProduct.lTensorHomToHomLTensor σ₁₂ P M₂ N₂ = TensorProduct.lift (LinearMap.llcomp R₂ P N₂ (TensorProduct R₂ M₂ N₂) ∘ₗ TensorProduct.mk R₂ M₂ N₂)
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The canonical linear map from (P →ₛₗ[σ₁₂] M₂) ⊗[R₂] N₂ to P →ₛₗ[σ₁₂] M₂ ⊗[R₂] N₂.
Equations
- TensorProduct.rTensorHomToHomRTensor σ₁₂ P M₂ N₂ = TensorProduct.lift (LinearMap.llcomp R₂ P M₂ (TensorProduct R₂ M₂ N₂) ∘ₗ (TensorProduct.mk R₂ M₂ N₂).flip).flip
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The linear map from (M →ₛₗ[σ₁₂] M₂) ⊗ (N →ₛₗ[σ₁₂] N₂) to M ⊗ N →ₛₗ[σ₁₂] M₂ ⊗ N₂
sending f ⊗ₜ g to TensorProduct.map f g, the tensor product of the two maps.
Equations
- TensorProduct.homTensorHomMap σ₁₂ M N M₂ N₂ = TensorProduct.lift (TensorProduct.mapBilinear σ₁₂ M N M₂ N₂)
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This is a binary version of TensorProduct.map: Given a bilinear map f : M ⟶ P ⟶ Q and a
bilinear map g : N ⟶ S ⟶ T, if we think f and g as semilinear maps with two inputs, then
map₂ f g is a bilinear map taking two inputs M ⊗ N → P ⊗ S → Q ⊗ S defined by
map₂ f g (m ⊗ n) (p ⊗ s) = f m p ⊗ g n s.
Mathematically, TensorProduct.map₂ is defined as the composition
M ⊗ N -map→ Hom(P, Q) ⊗ Hom(S, T) -homTensorHomMap→ Hom(P ⊗ S, Q ⊗ T).
Equations
- TensorProduct.map₂ f g = TensorProduct.homTensorHomMap σ₂₃ M₂ N₂ M₃ N₃ ∘ₛₗ TensorProduct.map f g
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If M and P are semilinearly equivalent and N and Q are semilinearly equivalent
then M ⊗ N and P ⊗ Q are semilinearly equivalent.
Equations
- TensorProduct.congr f g = LinearEquiv.ofLinear (TensorProduct.map ↑f ↑g) (TensorProduct.map ↑f.symm ↑g.symm) ⋯ ⋯
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LinearMap.lTensor M f : M ⊗ N →ₗ M ⊗ P is the natural linear map
induced by f : N →ₗ P.
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LinearMap.rTensor M f : N ⊗ M →ₗ P ⊗ M is the natural linear map
induced by f : N →ₗ P.
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Given a linear map f : N → P, f ⊗ M is injective if and only if M ⊗ f is injective.
Given a linear map f : N → P, f ⊗ M is surjective if and only if M ⊗ f is surjective.
Given a linear map f : N → P, f ⊗ M is bijective if and only if M ⊗ f is bijective.
lTensorHom M is the natural linear map that sends a linear map f : N →ₗ P to M ⊗ f.
See also Module.End.lTensorAlgHom.
Equations
- LinearMap.lTensorHom M = { toFun := LinearMap.lTensor M, map_add' := ⋯, map_smul' := ⋯ }
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rTensorHom M is the natural linear map that sends a linear map f : N →ₗ P to f ⊗ M.
See also Module.End.rTensorAlgHom.
Equations
- LinearMap.rTensorHom M = { toFun := fun (f : N →ₗ[R] P) => LinearMap.rTensor M f, map_add' := ⋯, map_smul' := ⋯ }
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LinearEquiv.lTensor M f : M ⊗ N ≃ₗ M ⊗ P is the natural linear equivalence
induced by f : N ≃ₗ P.
Equations
- LinearEquiv.lTensor M f = TensorProduct.congr (LinearEquiv.refl R M) f
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LinearEquiv.rTensor M f : N₁ ⊗ M ≃ₗ N₂ ⊗ M is the natural linear equivalence
induced by f : N₁ ≃ₗ N₂.
Equations
- LinearEquiv.rTensor M f = TensorProduct.congr f (LinearEquiv.refl R M)