Physlib

PhyslibAlpha.ProbabilisticTheory.JordanOrderUnit.Hom

Jordan homomorphisms

i. Overview

A Jordan homomorphism between unital real Jordan algebras is a real-linear unital map preserving the Jordan product.

ii. Key results

  • `JordanAlgebra.JordanHom` : Jordan homomorphisms.
  • `JordanAlgebra.JordanHom.comp` : composition.

14 declarations

instance

Coercion of JordanHom(E,F)\text{JordanHom}(E, F) to E→FE \to F

Given two unital real Jordan algebras EE and FF, an instance of `CoeFun` allows a Jordan homomorphism f∈JordanHom(E,F)f \in \text{JordanHom}(E, F) to be applied as a function from EE to FF.

theorem

Extensionality of Jordan homomorphisms

Let EE and FF be unital real Jordan algebras. For any two Jordan homomorphisms f,g:E→Ff, g: E \to F, if f(x)=g(x)f(x) = g(x) for all x∈Ex \in E, then f=gf = g.

theorem

Jordan homomorphisms map 00 to 00

Let EE and FF be real Jordan algebras. For any Jordan homomorphism f:E→Ff : E \to F, the image of the zero element in EE is the zero element in FF, that is, f(0)=0f(0) = 0.

theorem

f(x+y)=f(x)+f(y)f(x + y) = f(x) + f(y) for Jordan homomorphisms

Let EE and FF be unital real Jordan algebras, and let f:E→Ff: E \to F be a Jordan homomorphism. For any x,y∈Ex, y \in E, the map ff preserves addition, such that f(x+y)=f(x)+f(y)f(x + y) = f(x) + f(y).

theorem

f(r⋅x)=r⋅f(x)f(r \cdot x) = r \cdot f(x) for Jordan homomorphisms

Let EE and FF be unital real Jordan algebras, and let f:E→Ff: E \to F be a Jordan homomorphism. For any scalar r∈Rr \in \mathbb{R} and any element x∈Ex \in E, the image of the scalar multiplication r⋅xr \cdot x under ff is equal to r⋅f(x)r \cdot f(x).

theorem

f(1)=1f(1) = 1 for Jordan homomorphisms

Let EE and FF be unital real Jordan algebras. For any Jordan homomorphism f:E→Ff : E \to F, the image of the identity element 11 in EE is the identity element 11 in FF, that is, f(1)=1f(1) = 1.

theorem

Jordan Homomorphisms Preserve Jordan Products

Let EE and FF be unital real Jordan algebras. For any Jordan homomorphism f:E→Ff : E \to F and any elements x,y∈Ex, y \in E, the map preserves the Jordan product such that f(x⋅y)=f(x)⋅f(y)f(x \cdot y) = f(x) \cdot f(y).

definition

Identity Jordan homomorphism

For a unital real Jordan algebra EE, the identity Jordan homomorphism id:E→E\text{id}: E \to E is the map that sends every element x∈Ex \in E to itself. This map preserves the identity element (11) and the Jordan product.

definition

Composition of Jordan homomorphisms g∘fg \circ f

Given two unital real Jordan homomorphisms f:E→Ff: E \to F and g:F→Gg: F \to G between unital real Jordan algebras E,FE, F, and GG, their composition g∘fg \circ f is a unital real Jordan homomorphism from EE to GG.

theorem

id(x)=x\text{id}(x) = x for the identity Jordan homomorphism

For a unital real Jordan algebra EE and any element x∈Ex \in E, the identity Jordan homomorphism id:E→E\text{id} : E \to E applied to xx yields xx, that is, id(x)=x\text{id}(x) = x.

theorem

(g∘f)(x)=g(f(x))(g \circ f)(x) = g(f(x)) for Jordan homomorphisms

Let E,F,E, F, and GG be unital real Jordan algebras. For any Jordan homomorphisms f:E→Ff: E \to F and g:F→Gg: F \to G and any element x∈Ex \in E, the value of the composed homomorphism g∘fg \circ f at xx is equal to g(f(x))g(f(x)).

theorem

id∘f=f\text{id} \circ f = f for Jordan homomorphisms

Let EE and FF be unital real Jordan algebras. For any Jordan homomorphism f:E→Ff : E \to F, the composition of the identity Jordan homomorphism idF\text{id}_F on FF with ff is equal to ff. In mathematical notation, this is expressed as idF∘f=f\text{id}_F \circ f = f.

theorem

f∘id=ff \circ \text{id} = f for Jordan homomorphisms

Let EE and FF be unital real Jordan algebras. For any Jordan homomorphism f:E→Ff: E \to F, its composition with the identity Jordan homomorphism idE:E→E\text{id}_E: E \to E results in the original homomorphism ff, that is, f∘idE=ff \circ \text{id}_E = f.

theorem

Composition of Jordan homomorphisms is associative

Let E,FE, F, and GG be unital real Jordan algebras. For any Jordan homomorphisms (unital real-linear maps that preserve the Jordan product) f:E→Ff: E \to F, g:F→Gg: F \to G, and h:G→Eh: G \to E, the composition of these maps is associative: (h∘g)∘f=h∘(g∘f)(h \circ g) \circ f = h \circ (g \circ f)