Pi types of modules

This file defines constructors for linear maps whose domains or codomains are pi types.

It contains theorems relating these to each other, as well as to LinearMap.ker.

Main definitions

• pi types in the codomain:
  • LinearMap.pi
  • LinearMap.single
• pi types in the domain:
  • LinearMap.proj
  • LinearMap.diag

def LinearMap.pi {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) : M₂ →ₗ[R] (i : ι) → φ i

pi construction for linear functions. From a family of linear functions it produces a linear function into a family of modules.

Equations

• LinearMap.pi f = let __src := Pi.addHom fun (i : ι) => (f i).toAddHom; { toAddHom := { toFun := fun (c : M₂) (i : ι) => (f i) c, map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.pi_apply {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) (c : M₂) (i : ι) : (LinearMap.pi f) c i = (f i) c

theorem LinearMap.ker_pi {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) : LinearMap.ker (LinearMap.pi f) = ⨅ (i : ι), LinearMap.ker (f i)

theorem LinearMap.pi_eq_zero {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) : LinearMap.pi f = 0 ↔ ∀ (i : ι), f i = 0

theorem LinearMap.pi_zero {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] : (LinearMap.pi fun (i : ι) => 0) = 0

theorem LinearMap.pi_comp {R : Type u} {M₂ : Type w} {M₃ : Type y} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] [AddCommMonoid M₃] [Module R M₃] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) (g : M₃ →ₗ[R] M₂) : LinearMap.pi f ∘ₗ g = LinearMap.pi fun (i : ι) => f i ∘ₗ g

def LinearMap.proj {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (i : ι) : ((i : ι) → φ i) →ₗ[R] φ i

The projections from a family of modules are linear maps.

Note: known here as LinearMap.proj, this construction is in other categories called eval, for example Pi.evalMonoidHom, Pi.evalRingHom.

Equations

• LinearMap.proj i = { toAddHom := { toFun := Function.eval i, map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.coe_proj {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (i : ι) : ⇑(LinearMap.proj i) = Function.eval i

theorem LinearMap.proj_apply {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (i : ι) (b : (i : ι) → φ i) : (LinearMap.proj i) b = b i

theorem LinearMap.proj_pi {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (f : (i : ι) → M₂ →ₗ[R] φ i) (i : ι) : LinearMap.proj i ∘ₗ LinearMap.pi f = f i

theorem LinearMap.iInf_ker_proj {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] : ⨅ (i : ι), LinearMap.ker (LinearMap.proj i) = ⊥

instance LinearMap.CompatibleSMul.pi (R : Type u_1) (S : Type u_2) (M : Type u_3) (N : Type u_4) (ι : Type u_5) [Semiring S] [AddCommMonoid M] [AddCommMonoid N] [SMul R M] [SMul R N] [Module S M] [Module S N] [LinearMap.CompatibleSMul M N R S] : LinearMap.CompatibleSMul M (ι → N) R S

Equations

• ⋯ = ⋯

@[simp]

theorem LinearMap.compLeft_apply {R : Type u} {M₂ : Type w} {M₃ : Type y} [Semiring R] [AddCommMonoid M₂] [Module R M₂] [AddCommMonoid M₃] [Module R M₃] (f : M₂ →ₗ[R] M₃) (I : Type u_1) (h : I → M₂) : ∀ (a : I), (LinearMap.compLeft f I) h a = (⇑f ∘ h) a

def LinearMap.compLeft {R : Type u} {M₂ : Type w} {M₃ : Type y} [Semiring R] [AddCommMonoid M₂] [Module R M₂] [AddCommMonoid M₃] [Module R M₃] (f : M₂ →ₗ[R] M₃) (I : Type u_1) : (I → M₂) →ₗ[R] I → M₃

Linear map between the function spaces I → M₂ and I → M₃, induced by a linear map f between M₂ and M₃.

Equations

• LinearMap.compLeft f I = let __src := AddMonoidHom.compLeft (LinearMap.toAddMonoidHom f) I; { toAddHom := { toFun := fun (h : I → M₂) => ⇑f ∘ h, map_add' := ⋯ }, map_smul' := ⋯ }

theorem LinearMap.apply_single {R : Type u} {M : Type v} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [AddCommMonoid M] [Module R M] [DecidableEq ι] (f : (i : ι) → φ i →ₗ[R] M) (i : ι) (j : ι) (x : φ i) : (f j) (Pi.single i x j) = Pi.single i ((f i) x) j

def LinearMap.single {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [DecidableEq ι] (i : ι) : φ i →ₗ[R] (i : ι) → φ i

The LinearMap version of AddMonoidHom.single and Pi.single.

Equations

• LinearMap.single i = let __src := AddMonoidHom.single φ i; { toAddHom := { toFun := Pi.single i, map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.coe_single {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [DecidableEq ι] (i : ι) : ⇑(LinearMap.single i) = Pi.single i

@[simp]

theorem LinearMap.lsum_symm_apply (R : Type u) {M : Type v} {ι : Type x} [Semiring R] (φ : ι → Type i) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (S : Type u_1) [AddCommMonoid M] [Module R M] [Fintype ι] [DecidableEq ι] [Semiring S] [Module S M] [SMulCommClass R S M] (f : ((i : ι) → φ i) →ₗ[R] M) (i : ι) : (LinearEquiv.symm (LinearMap.lsum R φ S)) f i = LinearMap.comp f (LinearMap.single i)

def LinearMap.lsum (R : Type u) {M : Type v} {ι : Type x} [Semiring R] (φ : ι → Type i) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (S : Type u_1) [AddCommMonoid M] [Module R M] [Fintype ι] [DecidableEq ι] [Semiring S] [Module S M] [SMulCommClass R S M] : ((i : ι) → φ i →ₗ[R] M) ≃ₗ[S] ((i : ι) → φ i) →ₗ[R] M

The linear equivalence between linear functions on a finite product of modules and families of functions on these modules. See note [bundled maps over different rings].

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem LinearMap.lsum_apply (R : Type u) {M : Type v} {ι : Type x} [Semiring R] (φ : ι → Type i) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (S : Type u_1) [AddCommMonoid M] [Module R M] [Fintype ι] [DecidableEq ι] [Semiring S] [Module S M] [SMulCommClass R S M] (f : (i : ι) → φ i →ₗ[R] M) : (LinearMap.lsum R φ S) f = Finset.sum Finset.univ fun (i : ι) => f i ∘ₗ LinearMap.proj i

@[simp]

theorem LinearMap.lsum_single {ι : Type u_1} {R : Type u_2} [Fintype ι] [DecidableEq ι] [CommRing R] {M : ι → Type u_3} [(i : ι) → AddCommGroup (M i)] [(i : ι) → Module R (M i)] : (LinearMap.lsum R M R) LinearMap.single = LinearMap.id

theorem LinearMap.pi_ext {R : Type u} {M : Type v} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [Finite ι] [DecidableEq ι] [AddCommMonoid M] [Module R M] {f : ((i : ι) → φ i) →ₗ[R] M} {g : ((i : ι) → φ i) →ₗ[R] M} (h : ∀ (i : ι) (x : φ i), f (Pi.single i x) = g (Pi.single i x)) : f = g

theorem LinearMap.pi_ext_iff {R : Type u} {M : Type v} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [Finite ι] [DecidableEq ι] [AddCommMonoid M] [Module R M] {f : ((i : ι) → φ i) →ₗ[R] M} {g : ((i : ι) → φ i) →ₗ[R] M} : f = g ↔ ∀ (i : ι) (x : φ i), f (Pi.single i x) = g (Pi.single i x)

theorem LinearMap.pi_ext' {R : Type u} {M : Type v} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [Finite ι] [DecidableEq ι] [AddCommMonoid M] [Module R M] {f : ((i : ι) → φ i) →ₗ[R] M} {g : ((i : ι) → φ i) →ₗ[R] M} (h : ∀ (i : ι), f ∘ₗ LinearMap.single i = g ∘ₗ LinearMap.single i) : f = g

This is used as the ext lemma instead of LinearMap.pi_ext for reasons explained in note [partially-applied ext lemmas].

theorem LinearMap.pi_ext'_iff {R : Type u} {M : Type v} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [Finite ι] [DecidableEq ι] [AddCommMonoid M] [Module R M] {f : ((i : ι) → φ i) →ₗ[R] M} {g : ((i : ι) → φ i) →ₗ[R] M} : f = g ↔ ∀ (i : ι), f ∘ₗ LinearMap.single i = g ∘ₗ LinearMap.single i

def LinearMap.iInfKerProjEquiv (R : Type u) {ι : Type x} [Semiring R] (φ : ι → Type i) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {I : Set ι} {J : Set ι} [DecidablePred fun (i : ι) => i ∈ I] (hd : Disjoint I J) (hu : Set.univ ⊆ I ∪ J) : ↥(⨅ i ∈ J, LinearMap.ker (LinearMap.proj i)) ≃ₗ[R] (i : ↑I) → φ ↑i

If I and J are disjoint index sets, the product of the kernels of the Jth projections of φ is linearly equivalent to the product over I.

Equations

• One or more equations did not get rendered due to their size.

def LinearMap.diag {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [DecidableEq ι] (i : ι) (j : ι) : φ i →ₗ[R] φ j

diag i j is the identity map if i = j. Otherwise it is the constant 0 map.

Equations

• LinearMap.diag i j = Function.update 0 i LinearMap.id j

theorem LinearMap.update_apply {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] {φ : ι → Type i} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [DecidableEq ι] (f : (i : ι) → M₂ →ₗ[R] φ i) (c : M₂) (i : ι) (j : ι) (b : M₂ →ₗ[R] φ i) : (Function.update f i b j) c = Function.update (fun (i : ι) => (f i) c) i (b c) j

theorem LinearMap.pi_apply_eq_sum_univ {R : Type u} {M₂ : Type w} {ι : Type x} [Semiring R] [AddCommMonoid M₂] [Module R M₂] [Fintype ι] [DecidableEq ι] (f : (ι → R) →ₗ[R] M₂) (x : ι → R) : f x = Finset.sum Finset.univ fun (i : ι) => x i • f fun (j : ι) => if i = j then 1 else 0

A linear map f applied to x : ι → R can be computed using the image under f of elements of the canonical basis.

def Submodule.pi {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (I : Set ι) (p : (i : ι) → Submodule R (φ i)) : Submodule R ((i : ι) → φ i)

A version of Set.pi for submodules. Given an index set I and a family of submodules p : (i : ι) → Submodule R (φ i), pi I s is the submodule of dependent functions f : (i : ι) → φ i such that f i belongs to p a whenever i ∈ I.

Equations

• Submodule.pi I p = { toAddSubmonoid := { toAddSubsemigroup := { carrier := Set.pi I fun (i : ι) => ↑(p i), add_mem' := ⋯ }, zero_mem' := ⋯ }, smul_mem' := ⋯ }

@[simp]

theorem Submodule.mem_pi {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {I : Set ι} {p : (i : ι) → Submodule R (φ i)} {x : (i : ι) → φ i} : x ∈ Submodule.pi I p ↔ ∀ i ∈ I, x i ∈ p i

@[simp]

theorem Submodule.coe_pi {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {I : Set ι} {p : (i : ι) → Submodule R (φ i)} : ↑(Submodule.pi I p) = Set.pi I fun (i : ι) => ↑(p i)

@[simp]

theorem Submodule.pi_empty {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (p : (i : ι) → Submodule R (φ i)) : Submodule.pi ∅ p = ⊤

@[simp]

theorem Submodule.pi_top {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (s : Set ι) : (Submodule.pi s fun (i : ι) => ⊤) = ⊤

theorem Submodule.pi_mono {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {p : (i : ι) → Submodule R (φ i)} {q : (i : ι) → Submodule R (φ i)} {s : Set ι} (h : ∀ i ∈ s, p i ≤ q i) : Submodule.pi s p ≤ Submodule.pi s q

theorem Submodule.biInf_comap_proj {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {I : Set ι} {p : (i : ι) → Submodule R (φ i)} : ⨅ i ∈ I, Submodule.comap (LinearMap.proj i) (p i) = Submodule.pi I p

theorem Submodule.iInf_comap_proj {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {p : (i : ι) → Submodule R (φ i)} : ⨅ (i : ι), Submodule.comap (LinearMap.proj i) (p i) = Submodule.pi Set.univ p

theorem Submodule.iSup_map_single {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] {p : (i : ι) → Submodule R (φ i)} [DecidableEq ι] [Finite ι] : ⨆ (i : ι), Submodule.map (LinearMap.single i) (p i) = Submodule.pi Set.univ p

theorem Submodule.le_comap_single_pi {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [DecidableEq ι] (p : (i : ι) → Submodule R (φ i)) {i : ι} : p i ≤ Submodule.comap (LinearMap.single i) (Submodule.pi Set.univ p)

def LinearEquiv.piCongrRight {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} {ψ : ι → Type u_2} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [(i : ι) → AddCommMonoid (ψ i)] [(i : ι) → Module R (ψ i)] (e : (i : ι) → φ i ≃ₗ[R] ψ i) : ((i : ι) → φ i) ≃ₗ[R] (i : ι) → ψ i

Combine a family of linear equivalences into a linear equivalence of pi-types.

This is Equiv.piCongrRight as a LinearEquiv

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem LinearEquiv.piCongrRight_apply {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} {ψ : ι → Type u_2} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [(i : ι) → AddCommMonoid (ψ i)] [(i : ι) → Module R (ψ i)] (e : (i : ι) → φ i ≃ₗ[R] ψ i) (f : (i : ι) → φ i) (i : ι) : (LinearEquiv.piCongrRight e) f i = (e i) (f i)

@[simp]

theorem LinearEquiv.piCongrRight_refl {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] : (LinearEquiv.piCongrRight fun (j : ι) => LinearEquiv.refl R (φ j)) = LinearEquiv.refl R ((i : ι) → φ i)

@[simp]

theorem LinearEquiv.piCongrRight_symm {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} {ψ : ι → Type u_2} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [(i : ι) → AddCommMonoid (ψ i)] [(i : ι) → Module R (ψ i)] (e : (i : ι) → φ i ≃ₗ[R] ψ i) : LinearEquiv.symm (LinearEquiv.piCongrRight e) = LinearEquiv.piCongrRight fun (i : ι) => LinearEquiv.symm (e i)

@[simp]

theorem LinearEquiv.piCongrRight_trans {R : Type u} {ι : Type x} [Semiring R] {φ : ι → Type u_1} {ψ : ι → Type u_2} {χ : ι → Type u_3} [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] [(i : ι) → AddCommMonoid (ψ i)] [(i : ι) → Module R (ψ i)] [(i : ι) → AddCommMonoid (χ i)] [(i : ι) → Module R (χ i)] (e : (i : ι) → φ i ≃ₗ[R] ψ i) (f : (i : ι) → ψ i ≃ₗ[R] χ i) : LinearEquiv.piCongrRight e ≪≫ₗ LinearEquiv.piCongrRight f = LinearEquiv.piCongrRight fun (i : ι) => e i ≪≫ₗ f i

@[simp]

theorem LinearEquiv.piCongrLeft'_apply (R : Type u) {ι : Type x} {ι' : Type x'} [Semiring R] (φ : ι → Type u_1) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (e : ι ≃ ι') : ∀ (a : (a : ι) → φ a) (b : ι'), (LinearEquiv.piCongrLeft' R φ e) a b = a (e.symm b)

@[simp]

theorem LinearEquiv.piCongrLeft'_symm_apply (R : Type u) {ι : Type x} {ι' : Type x'} [Semiring R] (φ : ι → Type u_1) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (e : ι ≃ ι') : ∀ (a : (b : ι') → φ (e.symm b)) (a_1 : ι), (LinearEquiv.symm (LinearEquiv.piCongrLeft' R φ e)) a a_1 = ⋯ ▸ a (e a_1)

def LinearEquiv.piCongrLeft' (R : Type u) {ι : Type x} {ι' : Type x'} [Semiring R] (φ : ι → Type u_1) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (e : ι ≃ ι') : ((i' : ι) → φ i') ≃ₗ[R] (i : ι') → φ (e.symm i)

Transport dependent functions through an equivalence of the base space.

This is Equiv.piCongrLeft' as a LinearEquiv.

Equations

• One or more equations did not get rendered due to their size.

def LinearEquiv.piCongrLeft (R : Type u) {ι : Type x} {ι' : Type x'} [Semiring R] (φ : ι → Type u_1) [(i : ι) → AddCommMonoid (φ i)] [(i : ι) → Module R (φ i)] (e : ι' ≃ ι) : ((i' : ι') → φ (e i')) ≃ₗ[R] (i : ι) → φ i

Transporting dependent functions through an equivalence of the base, expressed as a "simplification".

This is Equiv.piCongrLeft as a LinearEquiv

Equations

• LinearEquiv.piCongrLeft R φ e = LinearEquiv.symm (LinearEquiv.piCongrLeft' R φ e.symm)

def LinearEquiv.piOptionEquivProd (R : Type u) [Semiring R] {ι : Type u_4} {M : Option ι → Type u_5} [(i : Option ι) → AddCommGroup (M i)] [(i : Option ι) → Module R (M i)] : ((i : Option ι) → M i) ≃ₗ[R] M none × ((i : ι) → M (some i))

This is Equiv.piOptionEquivProd as a LinearEquiv

Equations

• One or more equations did not get rendered due to their size.

def LinearEquiv.piRing (R : Type u) (M : Type v) (ι : Type x) [Semiring R] (S : Type u_4) [Fintype ι] [DecidableEq ι] [Semiring S] [AddCommMonoid M] [Module R M] [Module S M] [SMulCommClass R S M] : ((ι → R) →ₗ[R] M) ≃ₗ[S] ι → M

Linear equivalence between linear functions Rⁿ → M and Mⁿ. The spaces Rⁿ and Mⁿ are represented as ι → R and ι → M, respectively, where ι is a finite type.

This as an S-linear equivalence, under the assumption that S acts on M commuting with R. When R is commutative, we can take this to be the usual action with S = R. Otherwise, S = ℕ shows that the equivalence is additive. See note [bundled maps over different rings].

Equations

• LinearEquiv.piRing R M ι S = LinearEquiv.trans (LinearEquiv.symm (LinearMap.lsum R (fun (x : ι) => R) S)) (LinearEquiv.piCongrRight fun (x : ι) => LinearMap.ringLmapEquivSelf R S M)

@[simp]

theorem LinearEquiv.piRing_apply {R : Type u} {M : Type v} {ι : Type x} [Semiring R] (S : Type u_4) [Fintype ι] [DecidableEq ι] [Semiring S] [AddCommMonoid M] [Module R M] [Module S M] [SMulCommClass R S M] (f : (ι → R) →ₗ[R] M) (i : ι) : (LinearEquiv.piRing R M ι S) f i = f (Pi.single i 1)

@[simp]

theorem LinearEquiv.piRing_symm_apply {R : Type u} {M : Type v} {ι : Type x} [Semiring R] (S : Type u_4) [Fintype ι] [DecidableEq ι] [Semiring S] [AddCommMonoid M] [Module R M] [Module S M] [SMulCommClass R S M] (f : ι → M) (g : ι → R) : ((LinearEquiv.symm (LinearEquiv.piRing R M ι S)) f) g = Finset.sum Finset.univ fun (i : ι) => g i • f i

def LinearEquiv.sumArrowLequivProdArrow (α : Type u_5) (β : Type u_6) (R : Type u_7) (M : Type u_8) [Semiring R] [AddCommMonoid M] [Module R M] : (α ⊕ β → M) ≃ₗ[R] (α → M) × (β → M)

Equiv.sumArrowEquivProdArrow as a linear equivalence.

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem LinearEquiv.sumArrowLequivProdArrow_apply_fst {R : Type u} {M : Type v} [Semiring R] [AddCommMonoid M] [Module R M] {α : Type u_5} {β : Type u_6} (f : α ⊕ β → M) (a : α) : ((LinearEquiv.sumArrowLequivProdArrow α β R M) f).1 a = f (Sum.inl a)

@[simp]

theorem LinearEquiv.sumArrowLequivProdArrow_apply_snd {R : Type u} {M : Type v} [Semiring R] [AddCommMonoid M] [Module R M] {α : Type u_5} {β : Type u_6} (f : α ⊕ β → M) (b : β) : ((LinearEquiv.sumArrowLequivProdArrow α β R M) f).2 b = f (Sum.inr b)

@[simp]

theorem LinearEquiv.sumArrowLequivProdArrow_symm_apply_inl {R : Type u} {M : Type v} [Semiring R] [AddCommMonoid M] [Module R M] {α : Type u_5} {β : Type u_6} (f : α → M) (g : β → M) (a : α) : (LinearEquiv.symm (LinearEquiv.sumArrowLequivProdArrow α β R M)) (f, g) (Sum.inl a) = f a

@[simp]

theorem LinearEquiv.sumArrowLequivProdArrow_symm_apply_inr {R : Type u} {M : Type v} [Semiring R] [AddCommMonoid M] [Module R M] {α : Type u_5} {β : Type u_6} (f : α → M) (g : β → M) (b : β) : (LinearEquiv.symm (LinearEquiv.sumArrowLequivProdArrow α β R M)) (f, g) (Sum.inr b) = g b

@[simp]

theorem LinearEquiv.funUnique_symm_apply (ι : Type u_5) (R : Type u_6) (M : Type u_7) [Unique ι] [Semiring R] [AddCommMonoid M] [Module R M] : ⇑(LinearEquiv.symm (LinearEquiv.funUnique ι R M)) = uniqueElim

def LinearEquiv.funUnique (ι : Type u_5) (R : Type u_6) (M : Type u_7) [Unique ι] [Semiring R] [AddCommMonoid M] [Module R M] : (ι → M) ≃ₗ[R] M

If ι has a unique element, then ι → M is linearly equivalent to M.

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem LinearEquiv.funUnique_apply (ι : Type u_5) (R : Type u_6) (M : Type u_7) [Unique ι] [Semiring R] [AddCommMonoid M] [Module R M] : ⇑(LinearEquiv.funUnique ι R M) = Function.eval default

@[simp]

theorem LinearEquiv.piFinTwo_symm_apply (R : Type u) [Semiring R] (M : Fin 2 → Type v) [(i : Fin 2) → AddCommMonoid (M i)] [(i : Fin 2) → Module R (M i)] : ⇑(LinearEquiv.symm (LinearEquiv.piFinTwo R M)) = fun (p : M 0 × M 1) => Fin.cons p.1 (Fin.cons p.2 finZeroElim)

def LinearEquiv.piFinTwo (R : Type u) [Semiring R] (M : Fin 2 → Type v) [(i : Fin 2) → AddCommMonoid (M i)] [(i : Fin 2) → Module R (M i)] : ((i : Fin 2) → M i) ≃ₗ[R] M 0 × M 1

Linear equivalence between dependent functions (i : Fin 2) → M i and M 0 × M 1.

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem LinearEquiv.piFinTwo_apply (R : Type u) [Semiring R] (M : Fin 2 → Type v) [(i : Fin 2) → AddCommMonoid (M i)] [(i : Fin 2) → Module R (M i)] : ⇑(LinearEquiv.piFinTwo R M) = fun (f : (i : Fin 2) → M i) => (f 0, f 1)

@[simp]

theorem LinearEquiv.finTwoArrow_apply (R : Type u) (M : Type v) [Semiring R] [AddCommMonoid M] [Module R M] : ⇑(LinearEquiv.finTwoArrow R M) = fun (f : Fin 2 → M) => (f 0, f 1)

@[simp]

theorem LinearEquiv.finTwoArrow_symm_apply (R : Type u) (M : Type v) [Semiring R] [AddCommMonoid M] [Module R M] : ⇑(LinearEquiv.symm (LinearEquiv.finTwoArrow R M)) = fun (x : M × M) => ![x.1, x.2]

def LinearEquiv.finTwoArrow (R : Type u) (M : Type v) [Semiring R] [AddCommMonoid M] [Module R M] : (Fin 2 → M) ≃ₗ[R] M × M

Linear equivalence between vectors in M² = Fin 2 → M and M × M.

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem Function.ExtendByZero.linearMap_apply (R : Type u) {ι : Type x} {η : Type x} [Semiring R] (s : ι → η) (f : ι → R) : ∀ (a : η), (Function.ExtendByZero.linearMap R s) f a = Function.extend s f 0 a

noncomputable def Function.ExtendByZero.linearMap (R : Type u) {ι : Type x} {η : Type x} [Semiring R] (s : ι → η) : (ι → R) →ₗ[R] η → R

Function.extend s f 0 as a bundled linear map.

Equations

• Function.ExtendByZero.linearMap R s = let __src := Function.ExtendByZero.hom R s; { toAddHom := { toFun := fun (f : ι → R) => Function.extend s f 0, map_add' := ⋯ }, map_smul' := ⋯ }

Bundled versions of Matrix.vecCons and Matrix.vecEmpty

The idea of these definitions is to be able to define a map as x ↦ ![f₁ x, f₂ x, f₃ x], where f₁ f₂ f₃ are already linear maps, as f₁.vecCons <| f₂.vecCons <| f₃.vecCons <| vecEmpty.

While the same thing could be achieved using LinearMap.pi ![f₁, f₂, f₃], this is not definitionally equal to the result using LinearMap.vecCons, as Fin.cases and function application do not commute definitionally.

Versions for when f₁ f₂ f₃ are bilinear maps are also provided.

def LinearMap.vecEmpty {R : Type u} {M : Type v} {M₃ : Type y} [Semiring R] [AddCommMonoid M] [AddCommMonoid M₃] [Module R M] [Module R M₃] : M →ₗ[R] Fin 0 → M₃

The linear map defeq to Matrix.vecEmpty

Equations

• LinearMap.vecEmpty = { toAddHom := { toFun := fun (x : M) => ![], map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.vecEmpty_apply {R : Type u} {M : Type v} {M₃ : Type y} [Semiring R] [AddCommMonoid M] [AddCommMonoid M₃] [Module R M] [Module R M₃] (m : M) : LinearMap.vecEmpty m = ![]

def LinearMap.vecCons {R : Type u} {M : Type v} {M₂ : Type w} [Semiring R] [AddCommMonoid M] [AddCommMonoid M₂] [Module R M] [Module R M₂] {n : ℕ} (f : M →ₗ[R] M₂) (g : M →ₗ[R] Fin n → M₂) : M →ₗ[R] Fin (Nat.succ n) → M₂

A linear map into Fin n.succ → M₃ can be built out of a map into M₃ and a map into Fin n → M₃.

Equations

• LinearMap.vecCons f g = { toAddHom := { toFun := fun (m : M) => Matrix.vecCons (f m) (g m), map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.vecCons_apply {R : Type u} {M : Type v} {M₂ : Type w} [Semiring R] [AddCommMonoid M] [AddCommMonoid M₂] [Module R M] [Module R M₂] {n : ℕ} (f : M →ₗ[R] M₂) (g : M →ₗ[R] Fin n → M₂) (m : M) : (LinearMap.vecCons f g) m = Matrix.vecCons (f m) (g m)

@[simp]

theorem LinearMap.vecEmpty₂_apply {R : Type u} {M : Type v} {M₂ : Type w} {M₃ : Type y} [CommSemiring R] [AddCommMonoid M] [AddCommMonoid M₂] [AddCommMonoid M₃] [Module R M] [Module R M₂] [Module R M₃] : ∀ (x : M), LinearMap.vecEmpty₂ x = LinearMap.vecEmpty

def LinearMap.vecEmpty₂ {R : Type u} {M : Type v} {M₂ : Type w} {M₃ : Type y} [CommSemiring R] [AddCommMonoid M] [AddCommMonoid M₂] [AddCommMonoid M₃] [Module R M] [Module R M₂] [Module R M₃] : M →ₗ[R] M₂ →ₗ[R] Fin 0 → M₃

The empty bilinear map defeq to Matrix.vecEmpty

Equations

• LinearMap.vecEmpty₂ = { toAddHom := { toFun := fun (x : M) => LinearMap.vecEmpty, map_add' := ⋯ }, map_smul' := ⋯ }

@[simp]

theorem LinearMap.vecCons₂_apply {R : Type u} {M : Type v} {M₂ : Type w} {M₃ : Type y} [CommSemiring R] [AddCommMonoid M] [AddCommMonoid M₂] [AddCommMonoid M₃] [Module R M] [Module R M₂] [Module R M₃] {n : ℕ} (f : M →ₗ[R] M₂ →ₗ[R] M₃) (g : M →ₗ[R] M₂ →ₗ[R] Fin n → M₃) (m : M) : (LinearMap.vecCons₂ f g) m = LinearMap.vecCons (f m) (g m)

def LinearMap.vecCons₂ {R : Type u} {M : Type v} {M₂ : Type w} {M₃ : Type y} [CommSemiring R] [AddCommMonoid M] [AddCommMonoid M₂] [AddCommMonoid M₃] [Module R M] [Module R M₂] [Module R M₃] {n : ℕ} (f : M →ₗ[R] M₂ →ₗ[R] M₃) (g : M →ₗ[R] M₂ →ₗ[R] Fin n → M₃) : M →ₗ[R] M₂ →ₗ[R] Fin (Nat.succ n) → M₃

A bilinear map into Fin n.succ → M₃ can be built out of a map into M₃ and a map into Fin n → M₃

Equations

• LinearMap.vecCons₂ f g = { toAddHom := { toFun := fun (m : M) => LinearMap.vecCons (f m) (g m), map_add' := ⋯ }, map_smul' := ⋯ }