(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.
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.
Instances For
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.
- map_smulₛₗ (f : F) (r : R) (x : M) : f (r • x) = σ r • 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.
Instances For
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.
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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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.
Instances For
For a more powerful version, see coe_symm_mk'.
Equiv.cast (congrArg _ h) as a linear equiv.
Note that unlike Equiv.cast, this takes an equality of indices rather than an equality of types,
to avoid having to deal with an equality of the algebraic structure itself.
Instances For
An involutive linear map is a linear equivalence.
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Left scalar multiplication of a unit and a linear equivalence, as a linear equivalence.