Basics on bilinear maps #
This file provides basics on bilinear maps. The most general form considered are maps that are
semilinear in both arguments. They are of type M →ₛₗ[ρ₁₂] N →ₛₗ[σ₁₂] P, where M and N
are modules over R and S respectively, P is a module over both R₂ and S₂ with
commuting actions, and ρ₁₂ : R →+* R₂ and σ₁₂ : S →+* S₂.
Main declarations #
LinearMap.mk₂: a constructor for bilinear maps, taking an unbundled function together with proof witnesses of bilinearityLinearMap.flip: turns a bilinear mapM × N → PintoN × M → PLinearMap.lcompandLinearMap.llcomp: composition of linear maps as a bilinear mapLinearMap.compl₂: composition of a bilinear mapM × N → Pwith a linear mapQ → MLinearMap.compr₂: composition of a bilinear mapM × N → Pwith a linear mapQ → NLinearMap.lsmul: scalar multiplication as a bilinear mapR × M → M
Tags #
bilinear
Create a bilinear map from a function that is semilinear in each component.
See mk₂' and mk₂ for the linear case.
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Create a bilinear map from a function that is linear in each component.
See mk₂ for the special case where both arguments come from modules over the same ring.
Equations
- LinearMap.mk₂' R S f H1 H2 H3 H4 = LinearMap.mk₂'ₛₗ (RingHom.id R) (RingHom.id S) f H1 H2 H3 H4
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Given a linear map from M to linear maps from N to P, i.e., a bilinear map from M × N to
P, change the order of variables and get a linear map from N to linear maps from M to P.
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Restricting a bilinear map in the second entry
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Restricting a bilinear map in both components
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- LinearMap.domRestrict₁₂ f p q = LinearMap.domRestrict₂ (LinearMap.domRestrict f p) q
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Create a bilinear map from a function that is linear in each component.
This is a shorthand for mk₂' for the common case when R = S.
Equations
- LinearMap.mk₂ R f H1 H2 H3 H4 = LinearMap.mk₂' R R f H1 H2 H3 H4
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Given a linear map from M to linear maps from N to P, i.e., a bilinear map M → N → P,
change the order of variables and get a linear map from N to linear maps from M to P.
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Composing a linear map M → N and a linear map N → P to form a linear map M → P.
Equations
- LinearMap.lcomp R Pₗ f = LinearMap.flip (LinearMap.comp (LinearMap.flip LinearMap.id) f)
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Composing a semilinear map M → N and a semilinear map N → P to form a semilinear map
M → P is itself a linear map.
Equations
- LinearMap.lcompₛₗ P σ₂₃ f = LinearMap.flip (LinearMap.comp (LinearMap.flip LinearMap.id) f)
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Composing a linear map M → N and a linear map N → P to form a linear map M → P.
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Composing a linear map Q → N and a bilinear map M → N → P to
form a bilinear map M → Q → P.
Equations
- LinearMap.compl₂ f g = LinearMap.comp (LinearMap.lcompₛₗ P σ₂₃ g) f
Instances For
Composing linear maps Q → M and Q' → N with a bilinear map M → N → P to
form a bilinear map Q → Q' → P.
Equations
- LinearMap.compl₁₂ f g g' = LinearMap.compl₂ (LinearMap.comp f g) g'
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Composing a linear map P → Q and a bilinear map M → N → P to
form a bilinear map M → N → Q.
Equations
- LinearMap.compr₂ f g = LinearMap.comp (↑(LinearMap.llcomp R Nₗ Pₗ Qₗ) g) f
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Scalar multiplication as a bilinear map R → M → M.
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