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
The commutative associative subalgebra generated by
Given an element in a Jordan algebra over , the type `GeneratedByOne a` (denoted as ) is defined as the subtype of consisting of elements in the -submodule spanned by the set of Jordan powers , where and . While the ambient algebra is generally non-associative, is a commutative and associative unital -algebra.
Multiplication on
Given an element in a Jordan algebra , this definition provides the multiplication operation on the commutative associative subalgebra (the -submodule spanned by the Jordan powers ). For elements , their product is defined by the Jordan product in the ambient algebra .
The inclusion of into preserves multiplication
Let be a Jordan algebra over and . Let denote the commutative associative subalgebra of generated by the powers of . For any elements , the product as defined in is equal to the Jordan product in the ambient algebra .
Identity element of
This definition provides the multiplicative identity element for the subalgebra (represented by the type `GeneratedByOne a`), which is the -submodule of a Jordan algebra spanned by the powers of an element . The identity of the subalgebra is inherited from the identity element of the ambient algebra .
The identity of is the identity of
In a Jordan algebra over , let (represented by the type `GeneratedByOne a`) be the commutative associative subalgebra spanned by the Jordan powers of an element . The multiplicative identity element of the subalgebra is equal to the multiplicative identity element of the ambient Jordan algebra .
Multiplication in is associative
Let be a Jordan algebra over and be an element. Let denote the subalgebra generated by (defined as the -submodule spanned by the Jordan powers ). For any elements , the multiplication operation satisfies the associative law:
Commutativity of Multiplication in
Let be a Jordan algebra over and let be an element in . Let denote the subalgebra spanned by the Jordan powers of . For any elements , the multiplication operation is commutative, satisfying .
for
Let be an element of a Jordan algebra and let denote the commutative associative subalgebra generated by . For any element , the multiplicative identity of the subalgebra satisfies .
in the subalgebra
Let be an element of a Jordan algebra , and let denote the commutative associative unital -subalgebra generated by . For any element , it holds that , where is the identity element of .
Left Distributive Law in
Let be the commutative associative subalgebra of a Jordan algebra over spanned by the Jordan powers of an element . For any elements , the multiplication operation (inherited from the Jordan product) distributes over addition from the left:
Right Distributive Law in
Let be the commutative associative subalgebra of a Jordan algebra over spanned by the Jordan powers of an element . For any elements , the multiplication operation (inherited from the Jordan product) distributes over addition from the right:
is a commutative ring
Given a Jordan algebra over and an element , the subtype (represented by `GeneratedByOne a`), which is the -submodule of spanned by the Jordan powers , forms a commutative ring. The multiplication in this ring is defined by the Jordan product , which is associative when restricted to , and the identity element is the same as the identity of the ambient algebra .
Inclusion map
Given an element in a Jordan algebra over , let be the commutative associative unital -subalgebra generated by and the identity. This definition represents the natural inclusion map , which maps each element to its corresponding value in the ambient algebra .
Evaluation of the inclusion map at
Let be a Jordan algebra over and . Let be the commutative associative unital -subalgebra generated by and the identity. For any element , the inclusion map satisfies , where the right-hand side represents the element viewed as a member of the ambient algebra .
The inclusion map is injective
Let be a Jordan algebra over and . Let be the commutative associative unital -subalgebra generated by the powers of . Then the inclusion map is injective.
is an -algebra
Let be a Jordan algebra over and . The subtype (represented by `GeneratedByOne a`), which is the -submodule of spanned by the Jordan powers , is equipped with an -algebra structure. The algebra map is defined by , where is the identity element of . The scalar multiplication of on is inherited from the ambient module structure of and satisfies the identity , where denotes the Jordan product.
