FoxDifferential.Completed.FiniteStage.CoeffMap.BoundaryCycles
Fox Differential / Completed / Finite Stage / Coefficient Map / Boundary Cycles.
import
theorem finiteFoxStageSemidirectCoeffMap_left
(N : Subgroup (FreeGroup X)) [N.Normal] (hnm : n₀ ∣ m₀)
(y : FiniteFoxStageSemidirect (X := X) N m₀) :
(finiteFoxStageSemidirectCoeffMap (X := X) N hnm y).left =
fun i : X => finiteFoxStageTargetGroupAlgebraCoeffMap (X := X) N hnm (y.left i)The left component of finite-stage semidirect coefficient reduction is obtained by reducing each coordinate coefficient.
Show proof
rflProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_right
(N : Subgroup (FreeGroup X)) [N.Normal] (hnm : n₀ ∣ m₀)
(y : FiniteFoxStageSemidirect (X := X) N m₀) :
(finiteFoxStageSemidirectCoeffMap (X := X) N hnm y).right = y.rightThe right component of finite-stage semidirect coefficient reduction is unchanged.
Show proof
rflProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_rfl
(N : Subgroup (FreeGroup X)) [N.Normal] :
finiteFoxStageSemidirectCoeffMap
(X := X) (n₀ := n₀) (m₀ := n₀) N dvd_rfl =
MonoidHom.id (FiniteFoxStageSemidirect (X := X) N n₀)Coefficient reduction is the identity on finite-stage semidirect targets when the modulus is unchanged.
Show proof
by
apply MonoidHom.ext
intro y
apply FiniteFoxStageSemidirect.ext
· funext i
change finiteFoxStageTargetGroupAlgebraCoeffMap
(X := X) (n₀ := n₀) (m₀ := n₀) N dvd_rfl (y.left i) = y.left i
rw [finiteFoxStageTargetGroupAlgebraCoeffMap_rfl]
rfl
· rflProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_comp
{k₀ : ℕ} [Fact (0 < k₀)]
(N : Subgroup (FreeGroup X)) [N.Normal]
(hnm : n₀ ∣ m₀) (hmk : m₀ ∣ k₀) :
(finiteFoxStageSemidirectCoeffMap (X := X) N hnm).comp
(finiteFoxStageSemidirectCoeffMap (X := X) N hmk) =
finiteFoxStageSemidirectCoeffMap (X := X) N (dvd_trans hnm hmk)Coefficient reductions compose on finite-stage semidirect targets.
Show proof
by
apply MonoidHom.ext
intro y
apply FiniteFoxStageSemidirect.ext
· funext i
change finiteFoxStageTargetGroupAlgebraCoeffMap (X := X) N hnm
(finiteFoxStageTargetGroupAlgebraCoeffMap (X := X) N hmk (y.left i)) =
finiteFoxStageTargetGroupAlgebraCoeffMap (X := X) N (dvd_trans hnm hmk) (y.left i)
exact congrFun
(congrArg DFunLike.coe
(finiteFoxStageTargetGroupAlgebraCoeffMap_comp (X := X) N hnm hmk))
(y.left i)
· rflProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_mem_boundaryCycleSet
[Fintype X]
(N : Subgroup (FreeGroup X)) [N.Normal] (hnm : n₀ ∣ m₀)
{y : FiniteFoxStageSemidirect (X := X) N m₀}
(hy : y ∈ finiteFoxStageSemidirectBoundaryCycleSet (X := X) N m₀) :
finiteFoxStageSemidirectCoeffMap (X := X) N hnm y ∈
finiteFoxStageSemidirectBoundaryCycleSet (X := X) N n₀Show proof
by
rcases hy with ⟨hyright, hyboundary⟩
constructor
· simpa [finiteFoxStageSemidirectCoeffMap_right] using hyright
· simpa [finiteFoxStageSemidirectCoeffMap_left] using
finiteFoxStageBoundaryCycleSubmodule_coeffMap_mem
(X := X) N hnm hyboundaryProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_kernelWordPoint
(N : Subgroup (FreeGroup X)) [N.Normal] (hnm : n₀ ∣ m₀)
(w : FreeGroup X) :
finiteFoxStageSemidirectCoeffMap (X := X) N hnm
(finiteFoxStageSemidirectKernelWordPoint (X := X) N m₀ w) =
finiteFoxStageSemidirectKernelWordPoint (X := X) N n₀ wCoefficient reduction sends the finite semidirect kernel-word point at modulus \(m\) to the corresponding point at modulus \(n\).
Show proof
by
apply FiniteFoxStageSemidirect.ext
· funext i
change finiteFoxStageTargetGroupAlgebraCoeffMap (X := X) N hnm
(finiteFoxStageDerivative (X := X) N m₀ i w) =
finiteFoxStageDerivative (X := X) N n₀ i w
exact finiteFoxStageDerivative_coeffMap (X := X) N hnm i w
· rflProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
□theorem finiteFoxStageSemidirectCoeffMap_kernelWordDerivativeSet_subset
(N : Subgroup (FreeGroup X)) [N.Normal] (hnm : n₀ ∣ m₀) :
(fun y : FiniteFoxStageSemidirect (X := X) N m₀ =>
finiteFoxStageSemidirectCoeffMap (X := X) N hnm y) ''
finiteFoxStageSemidirectKernelWordDerivativeSet (X := X) N m₀ ⊆
finiteFoxStageSemidirectKernelWordDerivativeSet (X := X) N n₀Coefficient reduction sends the finite semidirect kernel-word derivative set at modulus \(m\) into the corresponding set at modulus \(n\).
Show proof
by
intro y hy
rcases hy with ⟨z, hz, rfl⟩
rcases hz with ⟨w, hwN, hzw⟩
refine ⟨w, hwN, ?_⟩
rw [← hzw]
exact (finiteFoxStageSemidirectCoeffMap_kernelWordPoint (X := X) N hnm w).symmProof. Work at the specified finite Fox stage. The quotient group and coefficient ring are finite, so all group-algebra expressions have finite support and the formulas are checked on group-like basis elements. The crossed-differential rule gives the product, inverse, derivative, and boundary identities; coefficient maps, quotient maps, source/target refinements, relation submodules, and semidirect constructions are then verified coordinatewise and extended by linearity. For stage systems or limit-comparison statements, compatibility under refinement and projection extensionality assemble the coordinate calculations.
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