Morphisms of star rings #
This file defines a new type of morphism between (non-unital) rings A and B where both
A and B are equipped with a star operation. This morphism, namely NonUnitalStarRingHom, is
a direct extension of its non-starred counterpart with a field map_star which guarantees it
preserves the star operation.
As with NonUnitalRingHom, the multiplications are not assumed to be associative or unital.
Main definitions #
Implementation #
This file is heavily inspired by Mathlib/Algebra/Star/StarAlgHom.lean.
Tags #
non-unital, ring, morphism, star
Non-unital star ring homomorphisms #
A non-unital ⋆-ring homomorphism is a non-unital ring homomorphism between non-unital
non-associative semirings A and B equipped with a star operation, and this homomorphism is
also star-preserving.
- toFun : A → B
By definition, a non-unital ⋆-ring homomorphism preserves the
staroperation.
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α →⋆ₙ+* β denotes the type of non-unital ring homomorphisms from α to β.
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NonUnitalStarRingHomClass F A B states that F is a type of non-unital ⋆-ring homomorphisms.
You should also extend this typeclass when you extend NonUnitalStarRingHom.
Instances
Turn an element of a type F satisfying NonUnitalStarRingHomClass F A B into an actual
NonUnitalStarRingHom. This is declared as the default coercion from F to A →⋆ₙ+ B.
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See Note [custom simps projection]
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Copy of a NonUnitalStarRingHom with a new toFun equal to the old one. Useful
to fix definitional equalities.
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The identity as a non-unital ⋆-ring homomorphism.
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The composition of non-unital ⋆-ring homomorphisms, as a non-unital ⋆-ring homomorphism.
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Star ring equivalences #
A ⋆-ring equivalence is an equivalence preserving addition, multiplication, and the star operation, which allows for considering both unital and non-unital equivalences with a single structure.
- 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 ⋆-ring equivalence preserves the
staroperation.
Instances For
A ⋆-ring equivalence is an equivalence preserving addition, multiplication, and the star operation, which allows for considering both unital and non-unital equivalences with a single structure.
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StarRingEquivClass F A B asserts F is a type of bundled ⋆-ring equivalences between A and
B.
You should also extend this typeclass when you extend StarRingEquiv.
By definition, a ⋆-ring equivalence preserves the
staroperation.
Instances
Turn an element of a type F satisfying StarRingEquivClass F A B into an actual
StarRingEquiv. This is declared as the default coercion from F to A ≃⋆+* B.
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Any type satisfying StarRingEquivClass can be cast into StarRingEquiv via
StarRingEquivClass.toStarRingEquiv.
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Auxiliary definition to avoid looping in dsimp with StarRingEquiv.symm_mk.
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If a (unital or non-unital) star ring morphism has an inverse, it is an isomorphism of star rings.
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Promote a bijective star ring homomorphism to a star ring equivalence.