The category of graded modules #
Let ๐ : โค โ Submodule k A be a family of k-submodules of a k-algebra A, typically the
pieces of a GradedAlgebra. A graded ๐-module is an A-module M with an internal
โค-grading M = โจโ Mโ by k-submodules, in the sense of TauCeti.InternalGrading, on which
๐ acts compatibly: ๐แตข โข Mโ โ M_{i+p}. A morphism of graded modules is an A-linear map of
degree zero, sending Mโ into Nโ for every p.
This file makes graded ๐-modules into a k-linear category TauCeti.GradedModuleCat ๐, with
a faithful additive forgetful functor to ModuleCat A, and constructs its grading shift
TauCeti.GradedModuleCat.shift ๐, the k-linear autoequivalence M โฆ M{1} of the category
with (M{1})โ = M_{p-1}. This is the convention under which the class of M{1} in a graded
Grothendieck group is q times the class of M, and it agrees with the shift of
TauCeti.GradedVectorSpace. Graded Grothendieck groups, graded Ext and graded Cartan maps of
graded algebras are formed in this category with this shift.
Main definitions #
TauCeti.GradedModuleCat ๐: the category of graded๐-modules.TauCeti.GradedModuleCat.ofHom: the morphism given by anA-linear map of degree zero.TauCeti.GradedModuleCat.isoMk: the isomorphism given by anA-linear equivalence which preserves and reflects degrees.TauCeti.GradedModuleCat.toModuleCat: the forgetful functor toModuleCat A.TauCeti.GradedModuleCat.shiftFunctor: the shiftM โฆ M{n}, with(M{n})โ = M_{p-n}.TauCeti.GradedModuleCat.shift: the grading shiftM โฆ M{1}, as an autoequivalence.
Main results #
TauCeti.GradedModuleCat.mem_shift_functor_obj_piece_iffandTauCeti.GradedModuleCat.mem_shift_inverse_obj_piece_iff:(M{1})โ = M_{p-1}and(M{-1})โ = M_{p+1}.
The category of graded ๐-modules: A-modules with an internal โค-grading by
k-submodules on which ๐แตข raises degrees by i.
- carrier : Type v
The underlying type of the module.
- isAddCommGroup : AddCommGroup self.carrier
- isScalarTower : IsScalarTower k A self.carrier
- grading : InternalGrading k self.carrier
The internal grading of the module.
- gradedSMul : SetLike.GradedSMul ๐ self.grading.piece
Instances For
The regular graded module of a graded algebra, with its given homogeneous pieces.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A morphism of graded ๐-modules: an A-linear map of degree zero.
The underlying
A-linear map.The underlying map sends
MโintoNโ.
Instances For
The morphism of graded modules given by an A-linear map of degree zero.
Equations
- TauCeti.GradedModuleCat.ofHom f hf = { hom := f, isHomogeneous := hf }
Instances For
A morphism of graded modules sends elements of degree p to elements of degree p.
Equations
- TauCeti.GradedModuleCat.instAddCommGroupHom = Function.Injective.addCommGroup (fun (f : M โถ N) => f.hom) โฏ โฏ โฏ โฏ โฏ โฏ โฏ
Equations
- TauCeti.GradedModuleCat.instModuleHom = Function.Injective.module k { toFun := fun (f : M โถ N) => f.hom, map_zero' := โฏ, map_add' := โฏ } โฏ โฏ
Equations
- TauCeti.GradedModuleCat.instPreadditive = { homGroup := inferInstance, add_comp := โฏ, comp_add := โฏ }
Equations
- TauCeti.GradedModuleCat.instLinear = { homModule := inferInstance, smul_comp := โฏ, comp_smul := โฏ }
The isomorphism of graded modules given by an A-linear equivalence which preserves and
reflects degrees.
Equations
- TauCeti.GradedModuleCat.isoMk e he = { hom := TauCeti.GradedModuleCat.ofHom โe โฏ, inv := TauCeti.GradedModuleCat.ofHom โe.symm โฏ, hom_inv_id := โฏ, inv_hom_id := โฏ }
Instances For
The forgetful functor from graded ๐-modules to A-modules.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The graded module M{n}: the module M with (M{n})โ = M_{p-n}.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A shift of a graded module has the same underlying k-module, so it is finite whenever the
module is.
The shift M โฆ M{n} of graded modules, the identity on underlying linear maps.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The grading shift M โฆ M{1} of graded ๐-modules, with (M{1})โ = M_{p-1}, as an
autoequivalence; its inverse is M โฆ M{-1}.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Forgetting the internal grading identifies every grading shift with the identity functor on underlying modules.
Equations
- TauCeti.GradedModuleCat.shiftFunctorCompToModuleCatIso n = CategoryTheory.NatIso.ofComponents (fun (M : TauCeti.GradedModuleCat ๐) => (LinearEquiv.refl A M.carrier).toModuleIso) โฏ