Physlib

PhyslibAlpha.AlgebraicFramework.JordanOrderUnit.JB.GeneratedByOne.Inherited

The inherited JB structure on a closed one-generator algebra

The closed algebra generated by one element is not merely a complete commutative normed algebra. It inherits the ambient order, order unit, square positivity, and JB square-norm law. This is the proper abstract input for the real Gelfand theorem needed by the Jordan continuous functional calculus: it retains the order information that distinguishes a formally real JB algebra from an arbitrary real uniform Banach algebra.

9 declarations

instance

CJ(a) C_J(a) is a normed Jordan algebra

Let E E be a normed Jordan algebra and let a∈E a \in E . The norm-closed Jordan subalgebra CJ(a)=J[a]‾ C_J(a) = \overline{J[a]} generated by the identity element 1 1 and a a is a normed Jordan algebra. It inherits the norm, addition, scalar multiplication, and the Jordan product x⋅y x \cdot y from the ambient algebra E E . Furthermore, while the multiplication in E E is generally non-associative, the multiplication restricted to CJ(a) C_J(a) is associative.

instance

EE is nontrivial   ⟹  CJ(a)\implies C_J(a) is nontrivial

Let EE be a nontrivial normed Jordan algebra. For any element a∈Ea \in E, the norm-closed Jordan subalgebra CJ(a)C_J(a) generated by the identity 11 and aa is also nontrivial.

instance

The identity element of CJ(a)C_J(a) has norm 11

Let EE be a nontrivial normed Jordan algebra and let a∈Ea \in E. In the norm-closed Jordan subalgebra CJ(a)C_J(a) generated by the identity element 11 and aa, the norm of the identity element is equal to 11, i.e., ∥1∥=1\|1\| = 1.

instance

CJ(a)C_J(a) is a JB algebra

Let EE be a JB algebra and let a∈Ea \in E. The norm-closed Jordan subalgebra CJ(a)C_J(a) (also denoted as J[a]‾\overline{J[a]}) generated by the identity element 11 and aa is itself a JB algebra.

instance

Positive real scalars preserve the order on CJ(a)C_J(a)

In the norm-closed Jordan subalgebra CJ(a)C_J(a) generated by the identity and an element aa of a normed Jordan algebra, scalar multiplication by non-negative real numbers preserves the partial order. That is, for any c∈Rc \in \mathbb{R} such that c≥0c \ge 0 and any elements x,y∈CJ(a)x, y \in C_J(a), if x≤yx \le y, then c⋅x≤c⋅yc \cdot x \le c \cdot y.

instance

11 is an order unit for CJ(a)C_J(a)

In a JB algebra EE, for any element a∈Ea \in E, the identity element 11 is an order unit for the norm-closed Jordan subalgebra CJ(a)C_J(a) generated by 11 and aa. This means that for every element x∈CJ(a)x \in C_J(a), there exists a real number c>0c > 0 such that −c⋅1≤x≤c⋅1-c \cdot 1 \le x \le c \cdot 1.

instance

CJ(a)C_J(a) is an Archimedean order unit space

Let EE be a JB algebra and let a∈Ea \in E. The norm-closed Jordan subalgebra CJ(a)=J[a]‾C_J(a) = \overline{J[a]} generated by the identity element 11 and aa is an Archimedean order unit space. This implies that the identity 11 is an order unit for CJ(a)C_J(a) and the partial order inherited by CJ(a)C_J(a) satisfies the Archimedean property.

instance

CJ(a)C_J(a) is a Jordan Order Unit Algebra

Let EE be a JB algebra and a∈Ea \in E. The norm-closed Jordan subalgebra CJ(a)=J[a]‾C_J(a) = \overline{J[a]} generated by the identity element 11 and aa is a Jordan order unit algebra. This means that CJ(a)C_J(a) is a Jordan algebra where the identity element 11 acts as an order unit and the square of any element x∈CJ(a)x \in C_J(a) is non-negative (x2≥0x^2 \ge 0).

instance

CJ(a)C_J(a) is a JB-order unit space

Let EE be a JB algebra and let a∈Ea \in E. The norm-closed Jordan subalgebra CJ(a)=J[a]‾C_J(a) = \overline{J[a]} generated by the identity element 11 and aa is a JB-order unit space. This signifies that CJ(a)C_J(a) inherits the compatibility between the norm and the order structure from the ambient algebra, where the norm is the order unit norm and the Jordan-specific norm-order laws are satisfied.