(Semi)linear equivalences #
In this file we define
LinearEquiv σ M M₂,M ≃ₛₗ[σ] M₂: an invertible semilinear map. Here,σis aRingHomfromRtoR₂and ane : M ≃ₛₗ[σ] M₂satisfiese (c • x) = (σ c) • (e x). The plain linear version, withσbeingRingHom.id R, is denoted byM ≃ₗ[R] M₂, and the star-linear version (withσbeingstarRingEnd) is denoted byM ≃ₗ⋆[R] M₂.
Implementation notes #
To ensure that composition works smoothly for semilinear equivalences, we use the typeclasses
RingHomCompTriple, RingHomInvPair and RingHomSurjective from
Algebra/Ring/CompTypeclasses.
The group structure on automorphisms, LinearEquiv.automorphismGroup, is provided elsewhere.
TODO #
- Parts of this file have not yet been generalized to semilinear maps
Tags #
linear equiv, linear equivalences, linear isomorphism, linear isomorphic
A linear equivalence is an invertible linear map.
- toFun : M → M₂
- invFun : M₂ → M
- left_inv : Function.LeftInverse self.invFun (↑self).toFun
- right_inv : Function.RightInverse self.invFun (↑self).toFun
Instances For
M ≃ₛₗ[σ] M₂ denotes the type of linear equivalences between M and M₂ over a
ring homomorphism σ.
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M ≃ₗ[R] M₂ denotes the type of linear equivalences between M and M₂ over
a plain linear map M →ₗ M₂.
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SemilinearEquivClass F σ M M₂ asserts F is a type of bundled σ-semilinear equivs
M → M₂.
See also LinearEquivClass F R M M₂ for the case where σ is the identity map on R.
A map f between an R-module and an S-module over a ring homomorphism σ : R →+* S
is semilinear if it satisfies the two properties f (x + y) = f x + f y and
f (c • x) = (σ c) • f x.
Applying a semilinear equivalence
foverσtor • xequalsσ r • f x.
Instances
LinearEquivClass F R M M₂ asserts F is a type of bundled R-linear equivs M → M₂.
This is an abbreviation for SemilinearEquivClass F (RingHom.id R) M M₂.
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Reinterpret an element of a type of semilinear equivalences as a semilinear equivalence.
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Reinterpret an element of a type of semilinear equivalences as a semilinear equivalence.
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The equivalence of types underlying a linear equivalence.
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The identity map is a linear equivalence.
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Linear equivalences are symmetric.
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See Note [custom simps projection]
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See Note [custom simps projection]
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Linear equivalences are transitive.
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Pretty printer defined by notation3 command.
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e₁ ≪≫ₗ e₂ denotes the composition of the linear equivalences e₁ and e₂.
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LinearEquiv.symm defines an equivalence between α ≃ₛₗ[σ] β and β ≃ₛₗ[σ] α.
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The two paths coercion can take to an AddMonoidHom are equivalent
Auxiliary definition to avoid looping in dsimp with LinearEquiv.symm_mk.
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An involutive linear map is a linear equivalence.