Nonnegatively graded quasicoherent algebras #
A nonnegatively graded algebra on a scheme X is a commutative monoid object in the symmetric
monoidal category of ℕ-graded 𝒪_X-modules. Requiring every homogeneous component to be
quasicoherent gives the category GradedQuasicoherentAlgebra X. Its morphisms are genuine graded
algebra morphisms, since they are morphisms of commutative monoid objects in graded modules.
The functor GradedQuasicoherentAlgebra.degree extracts any homogeneous component as a
quasicoherent sheaf. In particular, degreeOne is the coefficient object from which freely
generated graded algebras and their associated linear schemes are recovered. The unit
GradedQuasicoherentAlgebra.one and the homogeneous multiplications
GradedQuasicoherentAlgebra.mul are morphisms of quasicoherent sheaves between these
components, satisfying the unit, associativity and commutativity laws and preserved by morphisms
of graded algebras. These are the data transported along monoidal functors out of
quasicoherent sheaves, such as pullback.
Conversely, GradedQuasicoherentAlgebra.ofHomogeneous builds a graded quasicoherent algebra from
its homogeneous components, unit and homogeneous multiplications, and
GradedQuasicoherentAlgebra.homMk builds morphisms from componentwise maps. These are the
constructors through which graded algebras that are described degree by degree, such as
symmetric algebras of quasicoherent sheaves, enter this category.
Main declarations #
TauCeti.AlgebraicGeometry.isGradedQuasicoherentAlgebra: componentwise quasicoherence for a commutative algebra object in nonnegatively graded modules;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra: the full category cut out by that property;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.toGradedModules: the underlying graded module functor;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.hom_ext_of_epi_mul: morphisms out of a graded quasicoherent algebra generated in degree one are determined in degree one;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.degree: extraction of a homogeneous component as a quasicoherent sheaf;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.degreeOne: the degree-one functor;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.oneandTauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.mul: the unit and homogeneous multiplications as morphisms of quasicoherent sheaves, with their lawsone_mul,mul_one,mul_assoc,mul_comm,one_mapandmap_mul;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.ofHomogeneous: conversely, the graded quasicoherent algebra with given quasicoherent components, unit and homogeneous multiplications satisfying these laws;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.homMk: the morphism of graded quasicoherent algebras given by componentwise maps preserving the unit and the homogeneous multiplications;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.homMkOfEq: the same, for componentwise maps between families identified with the homogeneous components;TauCeti.AlgebraicGeometry.GradedQuasicoherentAlgebra.isoMkOfEq: the isomorphism given by componentwise isomorphisms between such families.
A commutative algebra object in nonnegatively graded 𝒪_X-modules is graded
quasicoherent when each of its homogeneous components is a quasicoherent 𝒪_X-module.
Instances For
A commutative algebra object in graded modules is graded quasicoherent exactly when each of its homogeneous components is quasicoherent.
The category of commutative nonnegatively graded quasicoherent 𝒪_X-algebras. Its morphisms
are morphisms of commutative monoid objects in graded modules, hence preserve the unit,
multiplication, and degree.
Instances For
Every homogeneous component of a graded quasicoherent algebra is quasicoherent.
The faithful functor forgetting the algebra structure while retaining the grading.
Instances For
Forgetting a graded quasicoherent algebra gives its underlying graded module.
Forgetting a graded algebra morphism gives its underlying morphism of graded modules.
Two morphisms of graded quasicoherent algebras agree when they agree in every degree.
Morphisms out of a graded quasicoherent algebra A generated in degree one are determined by
their degree-one components. Here generation in degree one means that the unit 𝒪_X ⟶ A₀ and
the multiplications Aₙ ⊗ A₁ ⟶ Aₙ₊₁ are epimorphisms, as for symmetric algebras.
Extract the degree-n component of a graded quasicoherent algebra as a quasicoherent sheaf.
On morphisms this is the degree-n component of the underlying graded algebra morphism.
Instances For
The underlying module of the degree-n component is the corresponding component of the
underlying graded module.
The degree functor acts on a graded algebra morphism by its component in that degree.
A morphism of graded quasicoherent algebras is an epimorphism in degree n when its image
under the degree-n functor is an epimorphism of the underlying modules.
Extract the degree-one component of a graded quasicoherent algebra. This is the component that generates a free graded algebra and therefore the coefficient sheaf of a linear scheme.
Instances For
The unit 𝒪_X ⟶ A₀ of a graded quasicoherent algebra, as a morphism of quasicoherent
sheaves into its degree-zero component.
Instances For
The homogeneous multiplication Aᵢ ⊗ Aⱼ ⟶ Aᵢ₊ⱼ of a graded quasicoherent algebra, as a
morphism of quasicoherent sheaves between its homogeneous components.
Instances For
The unit of A, as a morphism of quasicoherent sheaves, is the unit of the underlying graded
algebra on modules, up to the identification degree_obj_obj.
The homogeneous multiplication of A, as a morphism of quasicoherent sheaves, is that of the
underlying graded algebra on modules, up to the identifications degree_obj_obj.
The unit of a graded quasicoherent algebra is a left identity for homogeneous
multiplication, up to the identification of the degrees 0 + n and n.
The unit of a graded quasicoherent algebra is a left identity for homogeneous
multiplication, up to the identification of the degrees 0 + n and n.
The unit of a graded quasicoherent algebra is a right identity for homogeneous
multiplication, up to the identification of the degrees n + 0 and n.
The unit of a graded quasicoherent algebra is a right identity for homogeneous
multiplication, up to the identification of the degrees n + 0 and n.
Homogeneous multiplication of a graded quasicoherent algebra is associative, up to the
identification of the degrees i + j + k and i + (j + k).
Homogeneous multiplication of a graded quasicoherent algebra is associative, up to the
identification of the degrees i + j + k and i + (j + k).
Homogeneous multiplication of a graded quasicoherent algebra is commutative, up to the
identification of the degrees i + j and j + i.
Homogeneous multiplication of a graded quasicoherent algebra is commutative, up to the
identification of the degrees i + j and j + i.
A morphism of graded quasicoherent algebras preserves the unit in degree zero.
A morphism of graded quasicoherent algebras preserves the unit in degree zero.
A morphism of graded quasicoherent algebras commutes with homogeneous multiplication.
A morphism of graded quasicoherent algebras commutes with homogeneous multiplication.
The graded quasicoherent algebra with quasicoherent homogeneous components M n, unit
one : 𝒪_X ⟶ M 0 and homogeneous multiplications mul i j : M i ⊗ M j ⟶ M (i + j), which are
required to be unital, associative and commutative up to the identifications of degrees.
Instances For
The underlying graded module of ofHomogeneous is the given family of components.
The homogeneous multiplication of ofHomogeneous is the given one, up to the
identification ofHomogeneous_obj_X of its components with M.
The unit of ofHomogeneous is the given one, up to the identification
ofHomogeneous_obj_X of its degree-zero component with M 0.
A family of morphisms between the homogeneous components of two graded quasicoherent algebras which preserves the unit and the homogeneous multiplications is a morphism of graded quasicoherent algebras.
Instances For
The components of homMk f are the given morphisms.
A morphism of graded quasicoherent algebras whose homogeneous components are identified with
families M and N carrying units and multiplications, given by componentwise maps M n ⟶ N n
preserving those units and multiplications. This transports homMk along identifications of
components such as those provided by ofHomogeneous_obj_X.
Instances For
The components of homMkOfEq are the given morphisms, transported along the identifications
of the homogeneous components.
homMkOfEq sends a family of identities to the identity.
homMkOfEq sends componentwise composites to composites.
An isomorphism of graded quasicoherent algebras whose homogeneous components are identified
with families M and N carrying units and multiplications, given by componentwise isomorphisms
M n ≅ N n preserving those units and multiplications. Both directions are built by
homMkOfEq.
Instances For
The components of isoMkOfEq are the given isomorphisms, transported along the
identifications of the homogeneous components.
The components of the inverse of isoMkOfEq are the inverses of the given isomorphisms,
transported along the identifications of the homogeneous components.