Module: Mathlib.RingTheory.Invariant.Profinite

Goal state before:
pp: A : Type u_1
B : Type u_2
inst✝¹⁵ : CommRing A
inst✝¹⁴ : CommRing B
inst✝¹³ : Algebra A B
G : Type u
inst✝¹² : Group G
inst✝¹¹ : MulSemiringAction G B
inst✝¹⁰ : SMulCommClass G A B
inst✝⁹ : TopologicalSpace G
inst✝⁸ : CompactSpace G
inst✝⁷ : TotallyDisconnectedSpace G
inst✝⁶ : IsTopologicalGroup G
inst✝⁵ : TopologicalSpace B
inst✝⁴ : DiscreteTopology B
inst✝³ : ContinuousSMul G B
inst✝² : IsInvariant A B G
P Q : Ideal B
inst✝¹ : P.IsPrime
inst✝ : Q.IsPrime
hPQ : Ideal.under A P = Ideal.under A Q
B' : (G : Type u) → [inst : Monoid G] → [inst_1 : MulSemiringAction G B] → [SMulCommClass G A B] → Subalgebra A B :=
  FixedPoints.subalgebra A B
F : OpenNormalSubgroup G ⥤ Type u :=
  { obj := fun N ↦ { g // Ideal.under (↥(B' ↥↑N.toOpenSubgroup)) Q = g • Ideal.under (↥(B' ↥↑N.toOpenSubgroup)) P },
    map := fun {N N'} f ↦
      ↾fun x ↦ ⟨(QuotientGroup.map (↑N.toOpenSubgroup) N'.toOpenSubgroup.1 (MonoidHom.id G) ⋯) ↑x, ⋯⟩,
    map_id := ⋯, map_comp := ⋯ }
this✝ : ∀ (N : OpenNormalSubgroup G), Nonempty (F.obj N)
s : (j : OpenNormalSubgroup G) → F.obj j
hs : s ∈ F.sections
a : ↑(ProfiniteGrp.of G).toProfinite.toTop :=
  (ProfiniteGrp.Hom.hom (ProfiniteGrp.of G).isoLimittoFiniteQuotientFunctor.inv) ⟨fun N ↦ ↑(s N), ⋯⟩
this : ∀ (N : OpenNormalSubgroup G), ↑a = ↑(s N)
N : OpenNormalSubgroup G
x : ↥(B' ↥↑N.toOpenSubgroup)
hN : ↑N ⊆ ↑(MulAction.stabilizer G ↑x)
y : ↥(B' ↥↑N.toOpenSubgroup)
⊢ ((algebraMap (↥(B' ↥↑N.toOpenSubgroup)) B).comp
        ↑(RingEquiv.symm ((MulSemiringAction.toRingAut (G ⧸ ↑N.toOpenSubgroup) ↥(B' ↥↑N.toOpenSubgroup)) ↑(s N))))
      y =
    ((↑(RingEquiv.symm ((MulSemiringAction.toRingAut G B) a))).comp (algebraMap (↥(B' ↥↑N.toOpenSubgroup)) B)) y

Tactic:
simp [← this]

Goal state after:
A : Type u_1
B : Type u_2
inst✝¹⁵ : CommRing A
inst✝¹⁴ : CommRing B
inst✝¹³ : Algebra A B
G : Type u
inst✝¹² : Group G
inst✝¹¹ : MulSemiringAction G B
inst✝¹⁰ : SMulCommClass G A B
inst✝⁹ : TopologicalSpace G
inst✝⁸ : CompactSpace G
inst✝⁷ : TotallyDisconnectedSpace G
inst✝⁶ : IsTopologicalGroup G
inst✝⁵ : TopologicalSpace B
inst✝⁴ : DiscreteTopology B
inst✝³ : ContinuousSMul G B
inst✝² : IsInvariant A B G
P Q : Ideal B
inst✝¹ : P.IsPrime
inst✝ : Q.IsPrime
hPQ : Ideal.under A P = Ideal.under A Q
B' : (G : Type u) → [inst : Monoid G] → [inst_1 : MulSemiringAction G B] → [SMulCommClass G A B] → Subalgebra A B :=
  FixedPoints.subalgebra A B
F : OpenNormalSubgroup G ⥤ Type u :=
  { obj := fun N ↦ { g // Ideal.under (↥(B' ↥↑N.toOpenSubgroup)) Q = g • Ideal.under (↥(B' ↥↑N.toOpenSubgroup)) P },
    map := fun {N N'} f ↦
      ↾fun x ↦ ⟨(QuotientGroup.map (↑N.toOpenSubgroup) N'.toOpenSubgroup.1 (MonoidHom.id G) ⋯) ↑x, ⋯⟩,
    map_id := ⋯, map_comp := ⋯ }
this✝ : ∀ (N : OpenNormalSubgroup G), Nonempty (F.obj N)
s : (j : OpenNormalSubgroup G) → F.obj j
hs : s ∈ F.sections
a : ↑(ProfiniteGrp.of G).toProfinite.toTop :=
  (ProfiniteGrp.Hom.hom (ProfiniteGrp.of G).isoLimittoFiniteQuotientFunctor.inv) ⟨fun N ↦ ↑(s N), ⋯⟩
this : ∀ (N : OpenNormalSubgroup G), ↑a = ↑(s N)
N : OpenNormalSubgroup G
x : ↥(B' ↥↑N.toOpenSubgroup)
hN : ↑N ⊆ ↑(MulAction.stabilizer G ↑x)
y : ↥(B' ↥↑N.toOpenSubgroup)
⊢ ↑((↑a)⁻¹ • y) = a⁻¹ • ↑y