Differential and Algebras

This file defines derivations from a commutative ring to itself as a typeclass, which lets us use the x′ notation for the derivative of x.

class Differential (R : Type u_1) [CommRing R] : Type u_1

A derivation from a ring to itself, as a typeclass.

• deriv : Derivation ℤ R R

  The Derivation associated with the ring.

theorem Differential.ext_iff {R : Type u_1} {inst✝ : CommRing R} {x y : Differential R} : x = y ↔ deriv = deriv

theorem Differential.ext {R : Type u_1} {inst✝ : CommRing R} {x y : Differential R} (deriv : deriv = deriv) : x = y

def Differential.«term_′» : Lean.TrailingParserDescr

The Derivation associated with the ring.

def delabDeriv : Lean.PrettyPrinter.Delaborator.Delab

A delaborator for the x′ notation. This is required because it's not direct function application, so the default delaborator doesn't work.

class DifferentialAlgebra (A : Type u_1) (B : Type u_2) [CommRing A] [CommRing B] [Algebra A B] [Differential A] [Differential B] : Prop

A differential algebra is an Algebra where the derivation commutes with algebraMap.

• deriv_algebraMap (a : A) : ((algebraMap A B) a)′ = (algebraMap A B) a′

theorem algebraMap.coe_deriv {A : Type u_1} {B : Type u_2} [CommRing A] [CommRing B] [Algebra A B] [Differential A] [Differential B] [DifferentialAlgebra A B] (a : A) : ↑a′ = (↑a)′

class Differential.ContainConstants (A : Type u_1) (B : Type u_2) [CommRing A] [CommRing B] [Algebra A B] [Differential B] : Prop

A differential ring A and an algebra over it B share constants if all constants in B are in the range of algberaMap A B.

• mem_range_of_deriv_eq_zero {x : B} (h : x′ = 0) : x ∈ (algebraMap A B).range

  If the derivative of x is 0, then it's in the range of algberaMap A B.

theorem mem_range_of_deriv_eq_zero (A : Type u_1) {B : Type u_2} [CommRing A] [CommRing B] [Algebra A B] [Differential B] [Differential.ContainConstants A B] {x : B} (h : x′ = 0) : x ∈ (algebraMap A B).range

instance instDifferentialAlgebra (A : Type u_1) [CommRing A] [Differential A] : DifferentialAlgebra A A

instance instContainConstants (A : Type u_1) [CommRing A] [Differential A] : Differential.ContainConstants A A

@[reducible]

def Differential.equiv {R : Type u_1} {R₂ : Type u_2} [CommRing R] [CommRing R₂] [Differential R₂] (h : R ≃+* R₂) : Differential R

Transfer a Differential instance across a RingEquiv.

theorem DifferentialAlgebra.equiv {A : Type u_1} [CommRing A] [Differential A] {R : Type u_2} {R₂ : Type u_3} [CommRing R] [CommRing R₂] [Differential R₂] [Algebra A R] [Algebra A R₂] [DifferentialAlgebra A R₂] (h : R ≃ₐ[A] R₂) : DifferentialAlgebra A R

Transfer a DifferentialAlgebra instance across a AlgEquiv.