Physlib

PhyslibAlpha.AlgebraicFramework.JordanOrderUnit.StructureAlgebra

Jordan derivations and infinitesimal symmetries

This is the bundled companion to the generic predicate `IsDerivation`. A Jordan derivation is an infinitesimal reversible symmetry of an observable algebra; the module gives such generators a stable carrier, while `inner` packages commutators of multiplication operators. It is wholly algebraic and sits below order units, JB norms, Cstar realizations, and JBW normality.

The design is adapted from Cobord's `Jordan/StructureAlgebra.lean`, but reuses PhyslibAlpha's canonical `IsDerivation`, `innerDerivation`, and proved triple-commutator identities rather than introducing a parallel Jordan class or multiplication-operator API.

25 declarations

instance

Coercion of `JordanDerivation E` to E→EE \to E

This instance allows a Jordan derivation DD on a Jordan algebra EE to be treated as a function from EE to EE. It enables the notation D(x)D(x) for x∈Ex \in E, which evaluates the underlying linear map of the derivation at xx.

instance

Coercion from Jordan derivation to R\mathbb{R}-linear map

There is a canonical coercion that allows a Jordan derivation DD on a Jordan algebra EE to be treated as an R\mathbb{R}-linear map from EE to itself.

theorem

D1(x)=D2(x)  ⟹  D1=D2D_1(x) = D_2(x) \implies D_1 = D_2 for Jordan derivations

Let EE be a real vector space with a multiplication operation. If D1D_1 and D2D_2 are Jordan derivations on EE such that D1(x)=D2(x)D_1(x) = D_2(x) for all x∈Ex \in E, then D1=D2D_1 = D_2.

theorem

Leibniz Rule for Jordan Derivations: D(x⋅y)=D(x)⋅y+x⋅D(y)D(x \cdot y) = D(x) \cdot y + x \cdot D(y)

Let EE be a Jordan algebra and DD be a Jordan derivation on EE. For any elements x,y∈Ex, y \in E, the identity D(x⋅y)=D(x)⋅y+x⋅D(y)D(x \cdot y) = D(x) \cdot y + x \cdot D(y) holds, where ⋅\cdot denotes the Jordan product.

definition

Submodule of derivations Der(E)\text{Der}(E)

Let EE be a real vector space equipped with a multiplication operation. The set of all R\mathbb{R}-linear endomorphisms D:E→ED: E \to E that satisfy the Leibniz rule D(x⋅y)=D(x)⋅y+x⋅D(y)D(x \cdot y) = D(x) \cdot y + x \cdot D(y) for all x,y∈Ex, y \in E forms a submodule of the space of linear endomorphisms EndR(E)\text{End}_{\mathbb{R}}(E).

instance

Zero Jordan derivation 00

The zero element in the space of Jordan derivations on a real vector space EE is the derivation defined by the linear map D:E→ED : E \to E that maps every element x∈Ex \in E to 00. In the context of Jordan algebras, this represents the zero infinitesimal symmetry.

instance

Addition of Jordan derivations D1+D2 D_1 + D_2

Let E E be a Jordan algebra. For any two Jordan derivations D1,D2:E→E D_1, D_2: E \to E , their sum D1+D2 D_1 + D_2 is defined as the map (D1+D2)(x)=D1(x)+D2(x) (D_1 + D_2)(x) = D_1(x) + D_2(x) for all x∈E x \in E . This operation defines the addition for the type of Jordan derivations, where the sum of two linear maps satisfying the Leibniz rule is again a Jordan derivation.

instance

Negation of a Jordan derivation −D-D

Let EE be a Jordan algebra. For any Jordan derivation DD on EE, its negation −D-D is defined as the Jordan derivation whose underlying linear map is the pointwise negation of DD. That is, for all x∈Ex \in E, (−D)(x)=−(D(x))(-D)(x) = -(D(x)). This negation operation ensures that the set of Jordan derivations is closed under additive inversion.

theorem

0(x)=00(x) = 0 for Jordan derivations

Let EE be a Jordan algebra. For any element x∈Ex \in E, the zero Jordan derivation 0:E→E0 : E \to E maps xx to the zero element of EE, that is, 0(x)=00(x) = 0.

theorem

(D1+D2)(x)=D1(x)+D2(x)(D_1 + D_2)(x) = D_1(x) + D_2(x)

Let EE be a Jordan algebra. For any two Jordan derivations D1,D2D_1, D_2 on EE and any element x∈Ex \in E, the sum of the derivations D1+D2D_1 + D_2 satisfies (D1+D2)(x)=D1(x)+D2(x)(D_1 + D_2)(x) = D_1(x) + D_2(x).

theorem

Application of a negated Jordan derivation satisfies (−D)(x)=−D(x)(-D)(x) = -D(x)

Let EE be a Jordan algebra and DD be a Jordan derivation on EE. For any element x∈Ex \in E, the application of the negated derivation −D-D to xx is equal to the negation of the result of applying DD to xx, that is, (−D)(x)=−D(x)(-D)(x) = -D(x).

instance

Scalar multiplication of Jordan derivations by R\mathbb{R}

The scalar multiplication of a Jordan derivation DD on a Jordan algebra EE by a real number c∈Rc \in \mathbb{R} is defined such that for any x∈Ex \in E, (c⋅D)(x)=c⋅D(x)(c \cdot D)(x) = c \cdot D(x). This operation preserves the property of being a Jordan derivation (an infinitesimal reversible symmetry of the algebra).

theorem

(c⋅D)(x)=c⋅D(x)(c \cdot D)(x) = c \cdot D(x) for Jordan derivations

Let EE be a Jordan algebra. For any real number c∈Rc \in \mathbb{R}, any Jordan derivation DD on EE, and any element x∈Ex \in E, the application of the scalar multiple c⋅Dc \cdot D to xx satisfies (c⋅D)(x)=c⋅D(x)(c \cdot D)(x) = c \cdot D(x).

theorem

D(1)=0D(1) = 0 for Jordan derivations

Let EE be a Jordan algebra. For any Jordan derivation DD on EE, the identity element 11 is mapped to zero, such that D(1)=0D(1) = 0.

instance

Jordan derivations form an additive commutative group

Let EE be a Jordan algebra. The set of Jordan derivations on EE forms an additive commutative group (abelian group). The group operations are defined pointwise: for any Jordan derivations D,D1,D2D, D_1, D_2 and any x∈Ex \in E, the sum (D1+D2)(x)=D1(x)+D2(x)(D_1 + D_2)(x) = D_1(x) + D_2(x), the zero element 0(x)=00(x) = 0, and the negation (−D)(x)=−D(x)(-D)(x) = -D(x). These operations satisfy the standard axioms of an additive commutative group, including associativity (D1+D2)+D3=D1+(D2+D3)(D_1 + D_2) + D_3 = D_1 + (D_2 + D_3), commutativity D1+D2=D2+D1D_1 + D_2 = D_2 + D_1, and the existence of an additive identity and inverses.

instance

Jordan derivations form a real vector space

The set of Jordan derivations on a Jordan algebra EE forms a vector space over the field of real numbers R\mathbb{R}. This structure defines how Jordan derivations are scaled by real numbers and ensures that the collection of all such derivations satisfies the axioms of a real vector space (or R\mathbb{R}-module), including the distributivity of scalar multiplication over both derivation addition and real number addition, as well as the associativity of scalar multiplication.

definition

Commutator [D1,D2][D_1, D_2] of Jordan derivations

For any two Jordan derivations D1D_1 and D2D_2 on a Jordan algebra EE, their commutator [D1,D2][D_1, D_2] is defined as the linear map D1∘D2−D2∘D1D_1 \circ D_2 - D_2 \circ D_1. This commutator is itself a Jordan derivation.

theorem

comm(D1,D2)(x)=D1(D2(x))−D2(D1(x))\text{comm}(D_1, D_2)(x) = D_1(D_2(x)) - D_2(D_1(x))

For any two Jordan derivations D1D_1 and D2D_2 on a Jordan algebra EE, the commutator comm(D1,D2)\text{comm}(D_1, D_2) applied to an element x∈Ex \in E is equal to D1(D2(x))−D2(D1(x))D_1(D_2(x)) - D_2(D_1(x)).

instance

Commutator bracket ⟦⋅,⋅⟧\llbracket \cdot, \cdot \rrbracket for Jordan derivations

This instance defines the canonical bracket notation ⟦⋅,⋅⟧\llbracket \cdot, \cdot \rrbracket for the space of Jordan derivations on a Jordan algebra EE. For any two Jordan derivations D1D_1 and D2D_2, the bracket is given by the commutator ⟦D1,D2⟧=D1∘D2−D2∘D1\llbracket D_1, D_2 \rrbracket = D_1 \circ D_2 - D_2 \circ D_1.

theorem

⟦D1,D2⟧x=D1(D2x)−D2(D1x)\llbracket D_1, D_2 \rrbracket x = D_1(D_2 x) - D_2(D_1 x)

For any Jordan algebra EE, any two Jordan derivations D1,D2D_1, D_2 on EE, and any element x∈Ex \in E, the Lie bracket ⟦D1,D2⟧\llbracket D_1, D_2 \rrbracket applied to xx is given by the commutator formula ⟦D1,D2⟧x=D1(D2(x))−D2(D1(x))\llbracket D_1, D_2 \rrbracket x = D_1(D_2(x)) - D_2(D_1(x)).

instance

Jordan derivations form a Lie ring under the commutator ⟦⋅,⋅⟧\llbracket \cdot, \cdot \rrbracket

The set of Jordan derivations on a Jordan algebra EE forms a Lie ring. The Lie bracket ⟦D1,D2⟧\llbracket D_1, D_2 \rrbracket is defined as the commutator of derivations, given by ⟦D1,D2⟧=D1∘D2−D2∘D1\llbracket D_1, D_2 \rrbracket = D_1 \circ D_2 - D_2 \circ D_1. This structure satisfies the Lie ring axioms, including bi-additivity of the bracket, the alternating property ⟦D,D⟧=0\llbracket D, D \rrbracket = 0, and the Jacobi identity.

instance

Jordan derivations form a real Lie algebra

The set of Jordan derivations on a Jordan algebra EE forms a Lie algebra over the real numbers R\mathbb{R}. This structure equips the real vector space of Jordan derivations with a Lie bracket ⟦⋅,⋅⟧\llbracket \cdot, \cdot \rrbracket defined by the commutator of derivations, ⟦D1,D2⟧=D1∘D2−D2∘D1\llbracket D_1, D_2 \rrbracket = D_1 \circ D_2 - D_2 \circ D_1, satisfying the compatibility condition between scalar multiplication and the Lie bracket: c⋅⟦D1,D2⟧=⟦c⋅D1,D2⟧c \cdot \llbracket D_1, D_2 \rrbracket = \llbracket c \cdot D_1, D_2 \rrbracket for any c∈Rc \in \mathbb{R}.

definition

Inner Jordan derivation generated by aa and bb

Given two elements aa and bb in a Jordan algebra EE, the inner Jordan derivation inner(a,b)\text{inner}(a, b) is the derivation on EE defined by the action x↦a(bx)−b(ax)x \mapsto a(bx) - b(ax) for all x∈Ex \in E. This map corresponds to the commutator [La,Lb][L_a, L_b] of the left-multiplication operators LaL_a and LbL_b.

theorem

inner(a,b)(x)=a(bx)−b(ax)\text{inner}(a, b)(x) = a(bx) - b(ax)

Let EE be a Jordan algebra. For any elements a,b,x∈Ea, b, x \in E, the value of the inner derivation inner(a,b)\text{inner}(a, b) applied to xx is given by the formula: inner(a,b)(x)=a⋅(b⋅x)−b⋅(a⋅x)\text{inner}(a, b)(x) = a \cdot (b \cdot x) - b \cdot (a \cdot x) where ⋅\cdot denotes the Jordan product. This identity expresses the derivation as the commutator of the left-multiplication operators LaL_a and LbL_b acting on xx.

theorem

Commutator identity for inner Jordan derivations [inner(a,b),inner(c,d)][\text{inner}(a, b), \text{inner}(c, d)]

Let EE be a Jordan algebra. For any elements a,b,c,d∈Ea, b, c, d \in E, let inner(a,b)\text{inner}(a, b) denote the inner Jordan derivation generated by aa and bb, which acts on an element xx as inner(a,b)x=a(bx)−b(ax)\text{inner}(a, b)x = a(bx) - b(ax). The commutator of two such derivations satisfies the identity: [inner(a,b),inner(c,d)]=inner(inner(a,b)c,d)+inner(c,inner(a,b)d)[\text{inner}(a, b), \text{inner}(c, d)] = \text{inner}(\text{inner}(a, b)c, d) + \text{inner}(c, \text{inner}(a, b)d) where [δ1,δ2]=δ1∘δ2−δ2∘δ1[\delta_1, \delta_2] = \delta_1 \circ \delta_2 - \delta_2 \circ \delta_1 is the commutator of Jordan derivations.