(Semi-)linear isometries #
In this file we define LinearIsometry σ₁₂ E E₂
(notation: E →ₛₗᵢ[σ₁₂] E₂
) to be a semilinear
isometric embedding of E
into E₂
and LinearIsometryEquiv
(notation: E ≃ₛₗᵢ[σ₁₂] E₂
) to be
a semilinear isometric equivalence between E
and E₂
. The notation for the associated purely
linear concepts is E →ₗᵢ[R] E₂
, E ≃ₗᵢ[R] E₂
, and E →ₗᵢ⋆[R] E₂
, E ≃ₗᵢ⋆[R] E₂
for
the star-linear versions.
We also prove some trivial lemmas and provide convenience constructors.
Since a lot of elementary properties don't require ‖x‖ = 0 → x = 0
we start setting up the
theory for SeminormedAddCommGroup
and we specialize to NormedAddCommGroup
when needed.
A σ₁₂
-semilinear isometric embedding of a normed R
-module into an R₂
-module,
denoted as f : E →ₛₗᵢ[σ₁₂] E₂
.
- toFun : E → E₂
A σ₁₂
-semilinear isometric embedding of a normed R
-module into an R₂
-module,
denoted as f : E →ₛₗᵢ[σ₁₂] E₂
.
Equations
- One or more equations did not get rendered due to their size.
A linear isometric embedding of a normed R
-module into another one.
Equations
- One or more equations did not get rendered due to their size.
An antilinear isometric embedding of a normed R
-module into another one.
Equations
- One or more equations did not get rendered due to their size.
SemilinearIsometryClass F σ E E₂
asserts F
is a type of bundled σ
-semilinear isometries
E → E₂
.
See also LinearIsometryClass F R E E₂
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
.
Instances
LinearIsometryClass F R E E₂
asserts F
is a type of bundled R
-linear isometries
M → M₂
.
This is an abbreviation for SemilinearIsometryClass F (RingHom.id R) E E₂
.
Equations
- LinearIsometryClass 𝓕 R E E₂ = SemilinearIsometryClass 𝓕 (RingHom.id R) E E₂
Equations
- LinearIsometry.instFunLike = { coe := fun (f : E →ₛₗᵢ[σ₁₂] E₂) => f.toFun, coe_injective' := ⋯ }
See Note [custom simps projection]. We need to specify this projection explicitly in this case, because it is a composition of multiple projections.
Equations
- LinearIsometry.Simps.apply σ₁₂ E E₂ h = ⇑h
Alias of LinearIsometry.isEmbedding
.
Interpret a linear isometry as a continuous linear map.
Equations
- f.toContinuousLinearMap = { toLinearMap := f.toLinearMap, cont := ⋯ }
The identity linear isometry.
Equations
- LinearIsometry.id = { toLinearMap := LinearMap.id, norm_map' := ⋯ }
Equations
- LinearIsometry.instInhabited = { default := LinearIsometry.id }
Composition of linear isometries.
Equations
- g.comp f = { toLinearMap := g.toLinearMap ∘ₛₗ f.toLinearMap, norm_map' := ⋯ }
Equations
- LinearIsometry.instMonoid = { mul := LinearIsometry.comp, mul_assoc := ⋯, one := LinearIsometry.id, one_mul := ⋯, mul_one := ⋯, npow_zero := ⋯, npow_succ := ⋯ }
Construct a LinearIsometry
from a LinearMap
satisfying Isometry
.
Equations
- f.toLinearIsometry hf = { toLinearMap := f, norm_map' := ⋯ }
A semilinear isometric equivalence between two normed vector spaces,
denoted as f : E ≃ₛₗᵢ[σ₁₂] E₂
.
- toFun : E → E₂
- map_add' (x y : E) : (↑self.toLinearEquiv).toFun (x + y) = (↑self.toLinearEquiv).toFun x + (↑self.toLinearEquiv).toFun y
- map_smul' (m : R) (x : E) : (↑self.toLinearEquiv).toFun (m • x) = σ₁₂ m • (↑self.toLinearEquiv).toFun x
- invFun : E₂ → E
- left_inv : Function.LeftInverse self.invFun (↑self.toLinearEquiv).toFun
- right_inv : Function.RightInverse self.invFun (↑self.toLinearEquiv).toFun
A semilinear isometric equivalence between two normed vector spaces,
denoted as f : E ≃ₛₗᵢ[σ₁₂] E₂
.
Equations
- One or more equations did not get rendered due to their size.
A linear isometric equivalence between two normed vector spaces.
Equations
- One or more equations did not get rendered due to their size.
An antilinear isometric equivalence between two normed vector spaces.
Equations
- One or more equations did not get rendered due to their size.
SemilinearIsometryEquivClass F σ E E₂
asserts F
is a type of bundled σ
-semilinear
isometric equivs E → E₂
.
See also LinearIsometryEquivClass F R E E₂
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
.
Instances
LinearIsometryEquivClass F R E E₂
asserts F
is a type of bundled R
-linear isometries
M → M₂
.
This is an abbreviation for SemilinearIsometryEquivClass F (RingHom.id R) E E₂
.
Equations
- LinearIsometryEquivClass 𝓕 R E E₂ = SemilinearIsometryEquivClass 𝓕 (RingHom.id R) E E₂
Equations
- One or more equations did not get rendered due to their size.
Shortcut instance, saving 8.5% of compilation time in
Mathlib.Analysis.InnerProductSpace.Adjoint
.
(This instance was pinpointed by benchmarks; we didn't do an in depth investigation why it is specifically needed.)
Equations
- LinearIsometryEquiv.instCoeFun = { coe := DFunLike.coe }
Construct a LinearIsometryEquiv
from a LinearEquiv
and two inequalities:
∀ x, ‖e x‖ ≤ ‖x‖
and ∀ y, ‖e.symm y‖ ≤ ‖y‖
.
Equations
- LinearIsometryEquiv.ofBounds e h₁ h₂ = { toLinearEquiv := e, norm_map' := ⋯ }
Reinterpret a LinearIsometryEquiv
as a LinearIsometry
.
Equations
- e.toLinearIsometry = { toLinearMap := ↑e.toLinearEquiv, norm_map' := ⋯ }
Reinterpret a LinearIsometryEquiv
as an IsometryEquiv
.
Equations
- e.toIsometryEquiv = { toEquiv := e.toEquiv, isometry_toFun := ⋯ }
Reinterpret a LinearIsometryEquiv
as a Homeomorph
.
Equations
Interpret a LinearIsometryEquiv
as a ContinuousLinearEquiv
.
Equations
- One or more equations did not get rendered due to their size.
Identity map as a LinearIsometryEquiv
.
Equations
- LinearIsometryEquiv.refl R E = { toLinearEquiv := LinearEquiv.refl R E, norm_map' := ⋯ }
Linear isometry equiv between a space and its lift to another universe.
Equations
- LinearIsometryEquiv.ulift R E = { toLinearEquiv := ContinuousLinearEquiv.ulift.toLinearEquiv, norm_map' := ⋯ }
Equations
- LinearIsometryEquiv.instInhabited = { default := LinearIsometryEquiv.refl R E }
The inverse LinearIsometryEquiv
.
See Note [custom simps projection]. We need to specify this projection explicitly in this case, because it is a composition of multiple projections.
Equations
- LinearIsometryEquiv.Simps.apply σ₁₂ E E₂ h = ⇑h
See Note [custom simps projection]
Equations
- LinearIsometryEquiv.Simps.symm_apply σ₁₂ E E₂ h = ⇑h.symm
Composition of LinearIsometryEquiv
s as a LinearIsometryEquiv
.
Equations
- e.trans e' = { toLinearEquiv := e.trans e'.toLinearEquiv, norm_map' := ⋯ }
Equations
- One or more equations did not get rendered due to their size.
Lemmas about mixing the group structure with definitions. Because we have multiple ways to
express LinearIsometryEquiv.refl
, LinearIsometryEquiv.symm
, and
LinearIsometryEquiv.trans
, we want simp lemmas for every combination.
The assumption made here is that if you're using the group structure, you want to preserve it
after simp.
This copies the approach used by the lemmas near Equiv.Perm.trans_one
.
Reinterpret a LinearIsometryEquiv
as a ContinuousLinearEquiv
.
Equations
- LinearIsometryEquiv.instCoeTCContinuousLinearEquiv = { coe := fun (e : E ≃ₛₗᵢ[σ₁₂] E₂) => { toLinearEquiv := e.toLinearEquiv, continuous_toFun := ⋯, continuous_invFun := ⋯ } }
Equations
- LinearIsometryEquiv.instCoeTCContinuousLinearMap = { coe := fun (e : E ≃ₛₗᵢ[σ₁₂] E₂) => ↑{ toLinearEquiv := e.toLinearEquiv, continuous_toFun := ⋯, continuous_invFun := ⋯ } }
Construct a linear isometry equiv from a surjective linear isometry.
Equations
- LinearIsometryEquiv.ofSurjective f hfr = { toLinearEquiv := LinearEquiv.ofBijective f.toLinearMap ⋯, norm_map' := ⋯ }
If a linear isometry has an inverse, it is a linear isometric equivalence.
Equations
- LinearIsometryEquiv.ofLinearIsometry f g h₁ h₂ = { toLinearEquiv := LinearEquiv.ofLinear f.toLinearMap g h₁ h₂, norm_map' := ⋯ }
The negation operation on a normed space E
, considered as a linear isometry equivalence.
Equations
- LinearIsometryEquiv.neg R = { toLinearEquiv := LinearEquiv.neg R, norm_map' := ⋯ }
The natural equivalence (E × E₂) × E₃ ≃ E × (E₂ × E₃)
is a linear isometry.
Equations
- LinearIsometryEquiv.prodAssoc R E E₂ E₃ = { toLinearEquiv := LinearEquiv.prodAssoc R E E₂ E₃, norm_map' := ⋯ }
If p
is a submodule that is equal to ⊤
, then LinearIsometryEquiv.ofTop p hp
is the
"identity" equivalence between p
and E
.
Equations
- LinearIsometryEquiv.ofTop E p hp = { toLinearEquiv := LinearEquiv.ofTop p hp, norm_map' := ⋯ }
LinearEquiv.ofEq
as a LinearIsometryEquiv
.
Equations
- LinearIsometryEquiv.ofEq p q hpq = { toLinearEquiv := LinearEquiv.ofEq p q hpq, norm_map' := ⋯ }
Two linear isometries are equal if they are equal on basis vectors.
Two linear isometric equivalences are equal if they are equal on basis vectors.
Reinterpret a LinearIsometry
as a LinearIsometryEquiv
to the range.
Equations
- f.equivRange = { toLinearEquiv := LinearEquiv.ofInjective f.toLinearMap ⋯, norm_map' := ⋯ }