Physlib

PhyslibAlpha.ProbabilisticTheory.JordanOrderUnit.Power.Ring

`J[a]` is a commutative associative algebra

i. Overview

By power-associativity the Jordan product restricted to the span `J[a]` of the powers of `a` is associative. So `J[a]` is a commutative associative unital real algebra, to which Mathlib's theory of commutative algebras applies.

ii. Key results

  • `JordanAlgebra.GeneratedByOne` : the subalgebra `J[a]`.
  • `JordanAlgebra.GeneratedByOne.instCommRing` : its commutative ring structure.
  • `JordanAlgebra.GeneratedByOne.instAlgebra` : its real algebra structure.

iii. Table of contents

  • A. The carrier type and its multiplication
  • B. The commutative ring structure
  • C. The `ℝ`-algebra structure and inclusion

A. The carrier type and its multiplication

B. The commutative ring structure

C. The `ℝ`-algebra structure and inclusion

16 declarations

abbrev

The commutative associative subalgebra J[a]J[a] generated by aa

Given an element aa in a Jordan algebra EE over R\mathbb{R}, the type `GeneratedByOne a` (denoted as J[a]J[a]) is defined as the subtype of EE consisting of elements in the R\mathbb{R}-submodule spanned by the set of Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}}, where a0=1a^0 = 1 and an+1=a∘ana^{n+1} = a \circ a^n. While the ambient algebra EE is generally non-associative, J[a]J[a] is a commutative and associative unital R\mathbb{R}-algebra.

instance

Multiplication on J[a]J[a]

Given an element aa in a Jordan algebra EE, this definition provides the multiplication operation on the commutative associative subalgebra J[a]J[a] (the R\mathbb{R}-submodule spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}}). For elements x,y∈J[a]x, y \in J[a], their product is defined by the Jordan product x∘yx \circ y in the ambient algebra EE.

theorem

The inclusion of J[a]J[a] into EE preserves multiplication

Let EE be a Jordan algebra over R\mathbb{R} and a∈Ea \in E. Let J[a]J[a] denote the commutative associative subalgebra of EE generated by the powers of aa. For any elements x,y∈J[a]x, y \in J[a], the product x⋅yx \cdot y as defined in J[a]J[a] is equal to the Jordan product x∘yx \circ y in the ambient algebra EE.

instance

Identity element of J[a]J[a]

This definition provides the multiplicative identity element 11 for the subalgebra J[a]J[a] (represented by the type `GeneratedByOne a`), which is the R\mathbb{R}-submodule of a Jordan algebra EE spanned by the powers of an element aa. The identity of the subalgebra is inherited from the identity element of the ambient algebra EE.

theorem

The identity of J[a]J[a] is the identity of EE

In a Jordan algebra EE over R\mathbb{R}, let J[a]J[a] (represented by the type `GeneratedByOne a`) be the commutative associative subalgebra spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}} of an element a∈Ea \in E. The multiplicative identity element 11 of the subalgebra J[a]J[a] is equal to the multiplicative identity element 11 of the ambient Jordan algebra EE.

theorem

Multiplication in J[a]J[a] is associative

Let EE be a Jordan algebra over R\mathbb{R} and a∈Ea \in E be an element. Let J[a]J[a] denote the subalgebra generated by aa (defined as the R\mathbb{R}-submodule spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}}). For any elements x,y,z∈J[a]x, y, z \in J[a], the multiplication operation satisfies the associative law: (x⋅y)⋅z=x⋅(y⋅z)(x \cdot y) \cdot z = x \cdot (y \cdot z)

theorem

Commutativity of Multiplication in J[a]J[a]

Let EE be a Jordan algebra over R\mathbb{R} and let aa be an element in EE. Let J[a]J[a] denote the subalgebra spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}} of aa. For any elements x,y∈J[a]x, y \in J[a], the multiplication operation is commutative, satisfying x⋅y=y⋅xx \cdot y = y \cdot x.

theorem

1⋅x=x1 \cdot x = x for x∈J[a]x \in J[a]

Let aa be an element of a Jordan algebra EE and let J[a]J[a] denote the commutative associative subalgebra generated by aa. For any element x∈J[a]x \in J[a], the multiplicative identity 11 of the subalgebra satisfies 1⋅x=x1 \cdot x = x.

theorem

x⋅1=xx \cdot 1 = x in the subalgebra J[a]J[a]

Let aa be an element of a Jordan algebra EE, and let J[a]J[a] denote the commutative associative unital R\mathbb{R}-subalgebra generated by aa. For any element x∈J[a]x \in J[a], it holds that x⋅1=xx \cdot 1 = x, where 11 is the identity element of J[a]J[a].

theorem

Left Distributive Law in J[a]J[a]

Let J[a]J[a] be the commutative associative subalgebra of a Jordan algebra EE over R\mathbb{R} spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}} of an element a∈Ea \in E. For any elements x,y,z∈J[a]x, y, z \in J[a], the multiplication operation (inherited from the Jordan product) distributes over addition from the left: x⋅(y+z)=x⋅y+x⋅zx \cdot (y + z) = x \cdot y + x \cdot z

theorem

Right Distributive Law in J[a]J[a]

Let J[a]J[a] be the commutative associative subalgebra of a Jordan algebra EE over R\mathbb{R} spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}} of an element a∈Ea \in E. For any elements x,y,z∈J[a]x, y, z \in J[a], the multiplication operation (inherited from the Jordan product) distributes over addition from the right: (x+y)⋅z=x⋅z+y⋅z(x + y) \cdot z = x \cdot z + y \cdot z

instance

J[a]J[a] is a commutative ring

Given a Jordan algebra EE over R\mathbb{R} and an element a∈Ea \in E, the subtype J[a]J[a] (represented by `GeneratedByOne a`), which is the R\mathbb{R}-submodule of EE spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}}, forms a commutative ring. The multiplication in this ring is defined by the Jordan product x∘yx \circ y, which is associative when restricted to J[a]J[a], and the identity element is the same as the identity of the ambient algebra EE.

definition

Inclusion map J[a]↪EJ[a] \hookrightarrow E

Given an element aa in a Jordan algebra EE over R\mathbb{R}, let J[a]J[a] be the commutative associative unital R\mathbb{R}-subalgebra generated by aa and the identity. This definition represents the natural inclusion map J[a]↪EJ[a] \hookrightarrow E, which maps each element x∈J[a]x \in J[a] to its corresponding value in the ambient algebra EE.

theorem

Evaluation of the inclusion map ι:J[a]→E\iota: J[a] \to E at xx

Let EE be a Jordan algebra over R\mathbb{R} and a∈Ea \in E. Let J[a]J[a] be the commutative associative unital R\mathbb{R}-subalgebra generated by aa and the identity. For any element x∈J[a]x \in J[a], the inclusion map ι:J[a]→E\iota : J[a] \to E satisfies ι(x)=x\iota(x) = x, where the right-hand side represents the element xx viewed as a member of the ambient algebra EE.

theorem

The inclusion map J[a]↪EJ[a] \hookrightarrow E is injective

Let EE be a Jordan algebra over R\mathbb{R} and a∈Ea \in E. Let J[a]J[a] be the commutative associative unital R\mathbb{R}-subalgebra generated by the powers of aa. Then the inclusion map ι:J[a]→E\iota : J[a] \to E is injective.

instance

J[a]J[a] is an R\mathbb{R}-algebra

Let EE be a Jordan algebra over R\mathbb{R} and a∈Ea \in E. The subtype J[a]J[a] (represented by `GeneratedByOne a`), which is the R\mathbb{R}-submodule of EE spanned by the Jordan powers {an}n∈N\{a^n\}_{n \in \mathbb{N}}, is equipped with an R\mathbb{R}-algebra structure. The algebra map η:R→J[a]\eta: \mathbb{R} \to J[a] is defined by η(c)=c⋅1\eta(c) = c \cdot 1, where 11 is the identity element of EE. The scalar multiplication of c∈Rc \in \mathbb{R} on x∈J[a]x \in J[a] is inherited from the ambient module structure of EE and satisfies the identity c⋅x=(c⋅1)∘xc \cdot x = (c \cdot 1) \circ x, where ∘\circ denotes the Jordan product.