Morphisms of star algebras #
This file defines morphisms between R-algebras (unital or non-unital) A and B where both
A and B are equipped with a star operation. These morphisms, namely StarAlgHom and
NonUnitalStarAlgHom are direct extensions of their non-starred counterparts with a field
map_star which guarantees they preserve the star operation. We keep the type classes as generic
as possible, in keeping with the definition of NonUnitalAlgHom in the non-unital case. In this
file, we only assume Star unless we want to talk about the zero map as a
NonUnitalStarAlgHom, in which case we need StarAddMonoid. Note that the scalar ring R
is not required to have a star operation, nor do we need StarRing or StarModule structures on
A and B.
As with NonUnitalAlgHom, in the non-unital case the multiplications are not assumed to be
associative or unital, or even to be compatible with the scalar actions. In a typical application,
the operations will satisfy compatibility conditions making them into algebras (albeit possibly
non-associative and/or non-unital) but such conditions are not required here for the definitions.
The primary impetus for defining these types is that they constitute the morphisms in the categories
of unital C⋆-algebras (with StarAlgHoms) and of C⋆-algebras (with NonUnitalStarAlgHoms).
Main definitions #
Tags #
non-unital, algebra, morphism, star
Non-unital star algebra homomorphisms #
A non-unital ⋆-algebra homomorphism is a non-unital algebra homomorphism between
non-unital R-algebras A and B equipped with a star operation, and this homomorphism is
also star-preserving.
- toFun : A → B
By definition, a non-unital ⋆-algebra homomorphism preserves the
staroperation.
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A non-unital ⋆-algebra homomorphism is a non-unital algebra homomorphism between
non-unital R-algebras A and B equipped with a star operation, and this homomorphism is
also star-preserving.
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A non-unital ⋆-algebra homomorphism is a non-unital algebra homomorphism between
non-unital R-algebras A and B equipped with a star operation, and this homomorphism is
also star-preserving.
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Turn an element of a type F satisfying NonUnitalAlgHomClass F R A B and StarHomClass F A B
into an actual NonUnitalStarAlgHom. This is declared as the default coercion from F to
A →⋆ₙₐ[R] B.
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See Note [custom simps projection]
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Copy of a NonUnitalStarAlgHom with a new toFun equal to the old one. Useful
to fix definitional equalities.
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The identity as a non-unital ⋆-algebra homomorphism.
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The composition of non-unital ⋆-algebra homomorphisms, as a non-unital ⋆-algebra homomorphism.
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If a monoid R acts on another monoid S, then a non-unital star algebra homomorphism
over S can be viewed as a non-unital star algebra homomorphism over R.
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Unital star algebra homomorphisms #
A ⋆-algebra homomorphism is an algebra homomorphism between R-algebras A and B
equipped with a star operation, and this homomorphism is also star-preserving.
- toFun : A → B
By definition, a ⋆-algebra homomorphism preserves the
staroperation.
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A ⋆-algebra homomorphism is an algebra homomorphism between R-algebras A and B
equipped with a star operation, and this homomorphism is also star-preserving.
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A ⋆-algebra homomorphism is an algebra homomorphism between R-algebras A and B
equipped with a star operation, and this homomorphism is also star-preserving.
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Turn an element of a type F satisfying AlgHomClass F R A B and StarHomClass F A B into an
actual StarAlgHom. This is declared as the default coercion from F to A →⋆ₐ[R] B.
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Copy of a StarAlgHom with a new toFun equal to the old one. Useful
to fix definitional equalities.
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The identity as a StarAlgHom.
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algebraMap R A as a StarAlgHom when A is a star algebra over R.
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The composition of ⋆-algebra homomorphisms, as a ⋆-algebra homomorphism.
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Operations on the product type #
Note that this is copied from Algebra.Hom.NonUnitalAlg.
The first projection of a product is a non-unital ⋆-algebra homomorphism.
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The second projection of a product is a non-unital ⋆-algebra homomorphism.
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The Pi.prod of two morphisms is a morphism.
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Taking the product of two maps with the same domain is equivalent to taking the product of their codomains.
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Function.eval as a NonUnitalStarAlgHom.
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Function.eval as a StarAlgHom.
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The left injection into a product is a non-unital algebra homomorphism.
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The right injection into a product is a non-unital algebra homomorphism.
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The Pi.prod of two morphisms is a morphism.
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Taking the product of two maps with the same domain is equivalent to taking the product of their codomains.
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Star algebra equivalences #
A ⋆-algebra equivalence is an equivalence preserving addition, multiplication, scalar
multiplication and the star operation, which allows for considering both unital and non-unital
equivalences with a single structure. Currently, AlgEquiv requires unital algebras, which is
why this structure does not extend it.
- toFun : A → B
- invFun : B → A
- left_inv : Function.LeftInverse self.invFun self.toFun
- right_inv : Function.RightInverse self.invFun self.toFun
By definition, a ⋆-algebra equivalence preserves the
staroperation.By definition, a ⋆-algebra equivalence commutes with the action of scalars.
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A ⋆-algebra equivalence is an equivalence preserving addition, multiplication, scalar
multiplication and the star operation, which allows for considering both unital and non-unital
equivalences with a single structure. Currently, AlgEquiv requires unital algebras, which is
why this structure does not extend it.
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A ⋆-algebra equivalence is an equivalence preserving addition, multiplication, scalar
multiplication and the star operation, which allows for considering both unital and non-unital
equivalences with a single structure. Currently, AlgEquiv requires unital algebras, which is
why this structure does not extend it.
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The class that directly extends RingEquivClass and SMulHomClass.
Mostly an implementation detail for StarAlgEquivClass.
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Turn an element of a type F satisfying AlgEquivClass F R A B and StarHomClass F A B into
an actual StarAlgEquiv. This is declared as the default coercion from F to A ≃⋆ₐ[R] B.
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Any type satisfying AlgEquivClass and StarHomClass can be cast into StarAlgEquiv via
StarAlgEquivClass.toStarAlgEquiv.
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Auxiliary definition to avoid looping in dsimp with StarAlgEquiv.symm_mk.
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If a (unital or non-unital) star algebra morphism has an inverse, it is an isomorphism of star algebras.
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Promote a bijective star algebra homomorphism to a star algebra equivalence.