Non-unital Star Subalgebras #
In this file we define NonUnitalStarSubalgebras and the usual operations on them
(map, comap).
TODO #
- once we have scalar actions by semigroups (as opposed to monoids), implement the action of a non-unital subalgebra on the larger algebra.
If a type carries an involutive star, then any star-closed subset does too.
In a star magma (i.e., a multiplication with an antimultiplicative involutive star operation), any star-closed subset which is also closed under multiplication is itself a star magma.
In a StarAddMonoid (i.e., an additive monoid with an additive involutive star operation), any
star-closed subset which is also closed under addition and contains zero is itself a
StarAddMonoid.
In a star ring (i.e., a non-unital, non-associative, semiring with an additive, antimultiplicative, involutive star operation), a star-closed non-unital subsemiring is itself a star ring.
In a star R-module (i.e., star (r • m) = (star r) • m) any star-closed subset which is also
closed under the scalar action by R is itself a star R-module.
Embedding of a non-unital star subalgebra into the non-unital star algebra.
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A non-unital star subalgebra is a non-unital subalgebra which is closed under the star
operation.
The
carrierof aNonUnitalStarSubalgebrais closed under thestaroperation.
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The actual NonUnitalStarSubalgebra obtained from an element of a type satisfying
NonUnitalSubsemiringClass, SMulMemClass and StarMemClass.
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Copy of a non-unital star subalgebra with a new carrier equal to the old one.
Useful to fix definitional equalities.
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A non-unital star subalgebra over a ring is also a Subring.
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NonUnitalStarSubalgebras inherit structure from their NonUnitalSubsemiringClass and
NonUnitalSubringClass instances.
The forgetful map from NonUnitalStarSubalgebra to NonUnitalSubalgebra as an
OrderEmbedding
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NonUnitalStarSubalgebras inherit structure from their Submodule coercions.
Transport a non-unital star subalgebra via a non-unital star algebra homomorphism.
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Preimage of a non-unital star subalgebra under a non-unital star algebra homomorphism.
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A non-unital subalgebra closed under star is a non-unital star subalgebra.
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Range of an NonUnitalAlgHom as a NonUnitalStarSubalgebra.
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Restrict the codomain of a non-unital star algebra homomorphism.
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Restrict the codomain of a non-unital star algebra homomorphism f to f.range.
This is the bundled version of Set.rangeFactorization.
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The equalizer of two non-unital star R-algebra homomorphisms
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Restrict a non-unital star algebra homomorphism with a left inverse to an algebra isomorphism to its range.
This is a computable alternative to StarAlgEquiv.ofInjective.
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Restrict an injective non-unital star algebra homomorphism to a star algebra isomorphism
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The star closure of a subalgebra #
The pointwise star of a non-unital subalgebra is a non-unital subalgebra.
The star operation on NonUnitalSubalgebra commutes with NonUnitalAlgebra.adjoin.
The NonUnitalStarSubalgebra obtained from S : NonUnitalSubalgebra R A by taking the
smallest non-unital subalgebra containing both S and star S.
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The minimal non-unital subalgebra that includes s.
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Galois insertion between adjoin and SetLike.coe.
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NonUnitalStarAlgHom to ⊤ : NonUnitalStarSubalgebra R A.
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The map S → T when S is a non-unital star subalgebra contained in the non-unital star
algebra T.
This is the non-unital star subalgebra version of Submodule.inclusion, or
NonUnitalSubalgebra.inclusion
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The product of two non-unital star subalgebras is a non-unital star subalgebra.
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Define a non-unital star algebra homomorphism on a directed supremum of non-unital star subalgebras by defining it on each non-unital star subalgebra, and proving that it agrees on the intersection of non-unital star subalgebras.
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The center of a non-unital star algebra is the set of elements which commute with every element. They form a non-unital star subalgebra.
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The centralizer of the star-closure of a set as a non-unital star subalgebra.
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If all elements of s : Set A commute pairwise and with elements of star s, then adjoin R s
is commutative.
If all elements of s : Set A commute pairwise and with elements of star s, then adjoin R s
is a non-unital commutative semiring.
See note [reducible non-instances].
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If all elements of s : Set A commute pairwise and with elements of star s, then adjoin R s
is a non-unital commutative ring.
See note [reducible non-instances].