PhyslibAlpha.AlgebraicFramework.JordanOrderUnit.FreeSpecialTwo
The free special Jordan algebra on two generators
Let `A₂ = FreeAlgebra ℝ (Fin 2)`. Mathlib's `SymAlg A₂` is its normalized Jordanization, with product `x ∘ y = (xy + yx)/2`. The free special Jordan algebra on two generators is the Jordan fragment of that symmetrization generated by the two canonical free-associative letters.
This is only the concrete special side of Shirshov--Cohn. It deliberately does not claim that the abstract free Jordan algebra maps injectively here (Shirshov), nor that every quotient remains special (Cohn); those are the two distinct hard theorems to be formalized above this object.
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Free associative real algebra on two generators
The free associative algebra over the real numbers generated by two elements. This corresponds to the algebra of polynomials in two non-commuting variables with real coefficients.
is invertible in the free associative real algebra on two generators
In the free associative real algebra on two generators, the natural number is an invertible element. This is established by mapping the inverse of the real number into the algebra via the canonical algebra map .
Non-associative commutative ring structure on
The algebra , which is the symmetrization of the free associative algebra over on two generators, is equipped with the structure of a non-associative commutative ring. The addition is inherited from the underlying associative algebra, and the multiplication is the symmetrized Jordan product .
Scalar multiplication on
This definition provides a scalar multiplication of the Jordan algebra on itself. For any two elements , the scalar multiplication is defined as their product in the algebra, which is the symmetrized Jordan product derived from the underlying free associative algebra .
Scalar Tower Property for over
Let be the Jordanization of the free associative algebra over on two generators, where the Jordan product is defined as . For any scalar and elements , the scalar tower property holds.
in
In the Jordanization of the free associative real algebra on two generators, denoted by , scalar multiplication by real numbers commutes with the Jordan product. Specifically, for any scalar and any elements , the following equality holds: where denotes the symmetrized Jordan product defined as .
First generator of the free special Jordan algebra
The element representing the first canonical generator in the Jordanization of the free associative real algebra on two generators. The Jordanization, denoted , is the algebra equipped with the symmetrized Jordan product , and this definition identifies the first generator (index 0) of the underlying free associative algebra as an element of this Jordan algebra.
Second generator of the free special Jordan algebra
The element in the Jordanization of the free associative real algebra on two generators that corresponds to the second canonical generator . The Jordanization is the algebra equipped with the symmetrized Jordan product .
Submodule of the free special Jordan algebra on two generators
The -submodule of the Jordanization generated by the two canonical elements and . Here, is the free associative algebra over on two generators equipped with the symmetrized Jordan product . This submodule constitutes the carrier set of the free special Jordan algebra on two generators.
Free special Jordan algebra on two generators
The type representing the free special Jordan algebra on two generators. It is defined as the unital real Jordan subalgebra of generated by the two canonical elements and . Here, denotes the Jordanization of the free associative algebra over on two generators, equipped with the symmetrized Jordan product .
Let be the free associative algebra over on two generators, and let be its Jordanization with the symmetrized product . If is the first canonical generator (denoted `freeSpecialX`) and is the -submodule of generated by the two canonical generators, then .
The second generator belongs to the free special Jordan algebra on two generators
Let be the second canonical generator of the free associative algebra over on two generators. Let the free special Jordan algebra on two generators be the -submodule of the Jordanization (equipped with the symmetrized product ) generated by the two canonical elements and . Then is an element of this free special Jordan algebra.
Canonical generators of
This function maps the two indices of to the two canonical generators of the free special Jordan algebra on two generators. Specifically, index is mapped to the first generator and index is mapped to the second generator , both regarded as elements of the subalgebra .
Canonical homomorphism
The canonical unital Jordan homomorphism from the free unital real Jordan algebra on two generators, , to the free special Jordan algebra on two generators, . This map is defined using the universal property of the free Jordan algebra by sending its two abstract generators to the canonical generators and of the special Jordan algebra. Shirshov's theorem states that this homomorphism is injective.
The image of the first generator under the canonical homomorphism is
Let be the free unital real Jordan algebra on two generators and be the free special Jordan algebra on two generators. Let be the canonical unital Jordan homomorphism. Let be the first abstract generator of and be the first canonical generator of (associated with index 0). Then .
The canonical map sends the second generator to
Let be the free unital real Jordan algebra on two generators and be the free special Jordan algebra on two generators. Let be the canonical unital Jordan homomorphism. If is the second abstract generator and is the second canonical generator (indexed by ), then .
