FoxDifferential.Completed.CoefficientRings.CompletedGroupAlgebraModN.InClass.Augmentation
Fox Differential / Completed / Coefficient Rings / Completed Group Algebra Mod N / Within a Class / Augmentation.
Imported by
- FoxDifferential.Completed
- FoxDifferential.Completed.CoefficientRings
- FoxDifferential.Completed.CoefficientRings.CompletedGroupAlgebraModN
- FoxDifferential.Completed.CoefficientRings.CompletedGroupAlgebraModN.InClass
- FoxDifferential.Completed.CoefficientRings.CompletedGroupAlgebraModN.System.Basic
- FoxDifferential.Completed.ProCIntegerCoefficients.Augmentation
def modNCompletedGroupAlgebraStageAugmentationInClass
(C : ProCGroups.FiniteGroupClass.{u}) (U : CompletedGroupAlgebraIndexInClass G C) :
ModNCompletedGroupAlgebraStageInClass n G C U →+* ModNCompletedCoeff n :=
MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n)
(CompletedGroupAlgebraQuotientInClass G C U)
(1 : CompletedGroupAlgebraQuotientInClass G C U →* ModNCompletedCoeff n)The augmentation on one class-restricted residue-coefficient finite stage.
theorem modNCompletedGroupAlgebraStageAugmentationInClass_of
(C : ProCGroups.FiniteGroupClass.{u}) (U : CompletedGroupAlgebraIndexInClass G C)
(q : CompletedGroupAlgebraQuotientInClass G C U) :
modNCompletedGroupAlgebraStageAugmentationInClass n G C U
(MonoidAlgebra.of (ModNCompletedCoeff n) _ q) = 1The class-indexed finite-stage \(n\)-modular augmentation sends every group-like basis element to \(1\).
Show proof
by
classical
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, MonoidAlgebra.of, MonoidAlgebra.single,
MonoidHom.coe_mk, OneHom.coe_mk, RingHom.coe_coe, MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul,
mul_one]Proof. Unfold the mod-\(n\) completed group algebra as the inverse limit over finite group quotients with fixed coefficient ring \(\mathbb{Z}/n\mathbb{Z}\). Projections, transitions, augmentation, coefficient reduction, and algebra operations are computed coordinatewise at finite group-algebra stages. Compatibility under quotient refinement and inverse-limit extensionality assemble the completed statements.
□theorem modNCompletedGroupAlgebraStageAugmentationInClass_single
(C : ProCGroups.FiniteGroupClass.{u}) (U : CompletedGroupAlgebraIndexInClass G C)
(q : CompletedGroupAlgebraQuotientInClass G C U) (a : ModNCompletedCoeff n) :
modNCompletedGroupAlgebraStageAugmentationInClass n G C U
(MonoidAlgebra.single q a) = aThe class-indexed finite-stage \(n\)-modular augmentation sends a singleton basis element to its coefficient.
Show proof
by
classical
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, MonoidAlgebra.single, RingHom.coe_coe,
MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul, mul_one]Proof. Unfold the mod-\(n\) completed group algebra as the inverse limit over finite group quotients with fixed coefficient ring \(\mathbb{Z}/n\mathbb{Z}\). Projections, transitions, augmentation, coefficient reduction, and algebra operations are computed coordinatewise at finite group-algebra stages. Compatibility under quotient refinement and inverse-limit extensionality assemble the completed statements.
□theorem modNCompletedGroupAlgebraStageAugmentationInClass_compatible
(C : ProCGroups.FiniteGroupClass.{u})
{U V : CompletedGroupAlgebraIndexInClass G C} (hUV : U ≤ V) :
(modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraTransitionInClass n G C hUV) =
modNCompletedGroupAlgebraStageAugmentationInClass n G C VClass-indexed finite-stage \(n\)-modular augmentations are compatible with group-quotient transition maps.
Show proof
by
apply RingHom.ext
intro x
refine MonoidAlgebra.induction_on
(p := fun x =>
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraTransitionInClass n G C hUV)) x =
modNCompletedGroupAlgebraStageAugmentationInClass n G C V x)
x ?_ ?_ ?_
· intro q
rw [RingHom.comp_apply, modNCompletedGroupAlgebraTransitionInClass_of]
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, MonoidAlgebra.single, RingHom.coe_coe,
MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul, mul_one, MonoidAlgebra.of, MonoidHom.coe_mk,
OneHom.coe_mk]
· intro x y hx hy
simp only [RingHom.map_add, hx, hy]
· intro a x hx
rw [Algebra.smul_def, RingHom.map_mul, RingHom.map_mul, hx]
have hcoeff :
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraTransitionInClass n G C hUV))
(algebraMap (ModNCompletedCoeff n)
(ModNCompletedGroupAlgebraStageInClass n G C V) a) =
(modNCompletedGroupAlgebraStageAugmentationInClass n G C V)
(algebraMap (ModNCompletedCoeff n)
(ModNCompletedGroupAlgebraStageInClass n G C V) a) := by
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, modNCompletedGroupAlgebraTransitionInClass,
MonoidAlgebra.coe_algebraMap, Algebra.algebraMap_self, RingHom.coe_id, Function.comp_apply, id_eq,
RingHom.comp_apply, MonoidAlgebra.mapDomainRingHom_apply, Finsupp.mapDomain_single, map_one, RingHom.coe_coe,
MonoidAlgebra.lift_single, smul_eq_mul, mul_one]
rw [hcoeff]Proof. Unfold the mod-\(n\) completed group algebra as the inverse limit over finite group quotients with fixed coefficient ring \(\mathbb{Z}/n\mathbb{Z}\). Projections, transitions, augmentation, coefficient reduction, and algebra operations are computed coordinatewise at finite group-algebra stages. Compatibility under quotient refinement and inverse-limit extensionality assemble the completed statements.
□theorem modNCompletedGroupAlgebraStageAugmentationInClass_comp_stageMap
(C : ProCGroups.FiniteGroupClass.{u}) (U : CompletedGroupAlgebraIndexInClass G C) :
(modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U) =
MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n)Composing the class-indexed finite-stage \(n\)-modular augmentation with the dense stage map gives the ordinary \(n\)-modular group-algebra augmentation.
Show proof
by
apply RingHom.ext
intro x
refine MonoidAlgebra.induction_on
(p := fun x =>
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U)) x =
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n)) x)
x ?_ ?_ ?_
· intro g
rw [RingHom.comp_apply, modNCompletedGroupAlgebraStageMapInClass_of]
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, MonoidAlgebra.single, RingHom.coe_coe,
MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul, mul_one, MonoidAlgebra.of, MonoidHom.coe_mk,
OneHom.coe_mk]
· intro x y hx hy
simp only [hx, hy, map_add]
· intro a x hx
have hcoeff :
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) = a := by
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, modNCompletedGroupAlgebraStageMapInClass,
MonoidAlgebra.coe_algebraMap, Algebra.algebraMap_self, RingHom.coe_id, Function.comp_apply, id_eq,
RingHom.comp_apply, MonoidAlgebra.mapDomainRingHom_apply, Finsupp.mapDomain_single, map_one, RingHom.coe_coe,
MonoidAlgebra.lift_single, smul_eq_mul, mul_one]
have hcoeff' :
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) =
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) := by
rw [hcoeff]
simp only [MonoidAlgebra.coe_algebraMap, Algebra.algebraMap_self, RingHom.coe_id, Function.comp_apply, id_eq,
MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul, mul_one]
rw [Algebra.smul_def]
calc
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U))
((algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) * x)
=
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) *
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U)) x := by
rw [RingHom.map_mul]
_ =
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageMapInClass n G C U))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) *
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n)) x := by
rw [hx]
_ =
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) *
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n)) x := by
rw [hcoeff']
_ =
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n))
((algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) * x) := by
exact
(map_mul
(MonoidAlgebra.lift (ModNCompletedCoeff n) (ModNCompletedCoeff n) G
(1 : G →* ModNCompletedCoeff n))
(algebraMap (ModNCompletedCoeff n) (ModNCompletedGroupRing n G) a) x).symmProof. Unfold the mod-\(n\) completed group algebra as the inverse limit over finite group quotients with fixed coefficient ring \(\mathbb{Z}/n\mathbb{Z}\). Projections, transitions, augmentation, coefficient reduction, and algebra operations are computed coordinatewise at finite group-algebra stages. Compatibility under quotient refinement and inverse-limit extensionality assemble the completed statements.
□theorem modNCompletedGroupAlgebraStageAugmentationInClass_comp_stageCoeffMap
(C : ProCGroups.FiniteGroupClass.{u}) (U : CompletedGroupAlgebraIndexInClass G C)
{m : ℕ} [Fact (0 < m)] (hnm : n ∣ m) :
(modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageCoeffMapInClass
(n := n) (m := m) (G := G) C U hnm) =
(modNCompletedCoeffMap (n := n) (m := m) hnm).comp
(modNCompletedGroupAlgebraStageAugmentationInClass m G C U)Stage augmentations commute with coefficient reduction on class-restricted finite quotient stages.
Show proof
by
apply RingHom.ext
intro x
refine MonoidAlgebra.induction_on
(p := fun x =>
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageCoeffMapInClass
(n := n) (m := m) (G := G) C U hnm)) x =
((modNCompletedCoeffMap (n := n) (m := m) hnm).comp
(modNCompletedGroupAlgebraStageAugmentationInClass m G C U)) x)
x ?_ ?_ ?_
· intro q
rw [RingHom.comp_apply, RingHom.comp_apply,
modNCompletedGroupAlgebraStageCoeffMapInClass_of,
modNCompletedGroupAlgebraStageAugmentationInClass_of,
modNCompletedGroupAlgebraStageAugmentationInClass_of]
exact (map_one (modNCompletedCoeffMap (n := n) (m := m) hnm)).symm
· intro x y hx hy
simp only [RingHom.map_add, hx, RingHom.coe_comp, Function.comp_apply, hy]
· intro a x hx
letI : Algebra (ModNCompletedCoeff m) (ModNCompletedCoeff n) :=
ZMod.algebra' (R := ModNCompletedCoeff n) (m := n) (n := m) hnm
rw [Algebra.smul_def, RingHom.map_mul, RingHom.map_mul, hx]
have hcoeff :
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageCoeffMapInClass
(n := n) (m := m) (G := G) C U hnm))
(algebraMap (ModNCompletedCoeff m)
(ModNCompletedGroupAlgebraStageInClass m G C U) a) =
((modNCompletedCoeffMap (n := n) (m := m) hnm).comp
(modNCompletedGroupAlgebraStageAugmentationInClass m G C U))
(algebraMap (ModNCompletedCoeff m)
(ModNCompletedGroupAlgebraStageInClass m G C U) a) := by
have hleft :
((modNCompletedGroupAlgebraStageAugmentationInClass n G C U).comp
(modNCompletedGroupAlgebraStageCoeffMapInClass
(n := n) (m := m) (G := G) C U hnm))
(algebraMap (ModNCompletedCoeff m)
(ModNCompletedGroupAlgebraStageInClass m G C U) a) =
algebraMap (ModNCompletedCoeff m) (ModNCompletedCoeff n) a := by
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, modNCompletedGroupAlgebraStageCoeffMapInClass,
modNCompletedGroupRingCoeffMap, AlgHom.toRingHom_eq_coe, MonoidAlgebra.coe_algebraMap, Algebra.algebraMap_self,
RingHom.coe_id, Function.comp_apply, id_eq, RingHom.comp_apply, RingHom.coe_coe, MonoidAlgebra.lift_single,
MonoidAlgebra.of_apply, Algebra.smul_def, MonoidAlgebra.single_mul_single, mul_one,
MonoidHom.one_apply]
have hright :
((modNCompletedCoeffMap (n := n) (m := m) hnm).comp
(modNCompletedGroupAlgebraStageAugmentationInClass m G C U))
(algebraMap (ModNCompletedCoeff m)
(ModNCompletedGroupAlgebraStageInClass m G C U) a) =
algebraMap (ModNCompletedCoeff m) (ModNCompletedCoeff n) a := by
simp only [modNCompletedGroupAlgebraStageAugmentationInClass, MonoidAlgebra.coe_algebraMap,
Algebra.algebraMap_self, RingHom.coe_id, Function.comp_apply, id_eq, RingHom.comp_apply, RingHom.coe_coe,
MonoidAlgebra.lift_single, MonoidHom.one_apply, smul_eq_mul, mul_one]
rfl
exact hleft.trans hright.symm
rw [hcoeff]Proof. Unfold the mod-\(n\) completed group algebra as the inverse limit over finite group quotients with fixed coefficient ring \(\mathbb{Z}/n\mathbb{Z}\). Projections, transitions, augmentation, coefficient reduction, and algebra operations are computed coordinatewise at finite group-algebra stages. Compatibility under quotient refinement and inverse-limit extensionality assemble the completed statements.
□