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
Coercion of `JordanDerivation E` to
This instance allows a Jordan derivation on a Jordan algebra to be treated as a function from to . It enables the notation for , which evaluates the underlying linear map of the derivation at .
Coercion from Jordan derivation to -linear map
There is a canonical coercion that allows a Jordan derivation on a Jordan algebra to be treated as an -linear map from to itself.
for Jordan derivations
Let be a real vector space with a multiplication operation. If and are Jordan derivations on such that for all , then .
Leibniz Rule for Jordan Derivations:
Let be a Jordan algebra and be a Jordan derivation on . For any elements , the identity holds, where denotes the Jordan product.
Submodule of derivations
Let be a real vector space equipped with a multiplication operation. The set of all -linear endomorphisms that satisfy the Leibniz rule for all forms a submodule of the space of linear endomorphisms .
Zero Jordan derivation
The zero element in the space of Jordan derivations on a real vector space is the derivation defined by the linear map that maps every element to . In the context of Jordan algebras, this represents the zero infinitesimal symmetry.
Addition of Jordan derivations
Let be a Jordan algebra. For any two Jordan derivations , their sum is defined as the map for all . 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.
Negation of a Jordan derivation
Let be a Jordan algebra. For any Jordan derivation on , its negation is defined as the Jordan derivation whose underlying linear map is the pointwise negation of . That is, for all , . This negation operation ensures that the set of Jordan derivations is closed under additive inversion.
for Jordan derivations
Let be a Jordan algebra. For any element , the zero Jordan derivation maps to the zero element of , that is, .
Let be a Jordan algebra. For any two Jordan derivations on and any element , the sum of the derivations satisfies .
Application of a negated Jordan derivation satisfies
Let be a Jordan algebra and be a Jordan derivation on . For any element , the application of the negated derivation to is equal to the negation of the result of applying to , that is, .
Scalar multiplication of Jordan derivations by
The scalar multiplication of a Jordan derivation on a Jordan algebra by a real number is defined such that for any , . This operation preserves the property of being a Jordan derivation (an infinitesimal reversible symmetry of the algebra).
for Jordan derivations
Let be a Jordan algebra. For any real number , any Jordan derivation on , and any element , the application of the scalar multiple to satisfies .
for Jordan derivations
Let be a Jordan algebra. For any Jordan derivation on , the identity element is mapped to zero, such that .
Jordan derivations form an additive commutative group
Let be a Jordan algebra. The set of Jordan derivations on forms an additive commutative group (abelian group). The group operations are defined pointwise: for any Jordan derivations and any , the sum , the zero element , and the negation . These operations satisfy the standard axioms of an additive commutative group, including associativity , commutativity , and the existence of an additive identity and inverses.
Jordan derivations form a real vector space
The set of Jordan derivations on a Jordan algebra forms a vector space over the field of real numbers . 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 -module), including the distributivity of scalar multiplication over both derivation addition and real number addition, as well as the associativity of scalar multiplication.
Commutator of Jordan derivations
For any two Jordan derivations and on a Jordan algebra , their commutator is defined as the linear map . This commutator is itself a Jordan derivation.
For any two Jordan derivations and on a Jordan algebra , the commutator applied to an element is equal to .
Commutator bracket for Jordan derivations
This instance defines the canonical bracket notation for the space of Jordan derivations on a Jordan algebra . For any two Jordan derivations and , the bracket is given by the commutator .
For any Jordan algebra , any two Jordan derivations on , and any element , the Lie bracket applied to is given by the commutator formula .
Jordan derivations form a Lie ring under the commutator
The set of Jordan derivations on a Jordan algebra forms a Lie ring. The Lie bracket is defined as the commutator of derivations, given by . This structure satisfies the Lie ring axioms, including bi-additivity of the bracket, the alternating property , and the Jacobi identity.
Jordan derivations form a real Lie algebra
The set of Jordan derivations on a Jordan algebra forms a Lie algebra over the real numbers . This structure equips the real vector space of Jordan derivations with a Lie bracket defined by the commutator of derivations, , satisfying the compatibility condition between scalar multiplication and the Lie bracket: for any .
Inner Jordan derivation generated by and
Given two elements and in a Jordan algebra , the inner Jordan derivation is the derivation on defined by the action for all . This map corresponds to the commutator of the left-multiplication operators and .
Let be a Jordan algebra. For any elements , the value of the inner derivation applied to is given by the formula: where denotes the Jordan product. This identity expresses the derivation as the commutator of the left-multiplication operators and acting on .
Commutator identity for inner Jordan derivations
Let be a Jordan algebra. For any elements , let denote the inner Jordan derivation generated by and , which acts on an element as . The commutator of two such derivations satisfies the identity: where is the commutator of Jordan derivations.
