Module

GroupSystemRestriction.lean

Nyll.ProCGroups.InverseSystems.GroupSystemRestriction
2 declarations indexed from sourceView source ↗

Group structures on restricted inverse systems

The existing restriction keeps the stage groups and transition homomorphisms. This canonical instance permits both homomorphisms to the restricted limit and its coordinatewise group laws to use the original inverse-system owner.

Declarations

ProCGroups.InverseSystems.InverseSystem.restrict_groups
Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

namespace ProCGroups.InverseSystems
universe u v
variable {I : Type u} [Preorder I] (S : InverseSystem.{u, v} (I := I))
  [∀ i, Group (S.X i)] [IsGroupSystem S]
instance InverseSystem.restrict_groups (J : Set I) :
    ∀ j : J, Group ((S.restrict J).X j)
ProCGroups.InverseSystems.InverseSystem.restrict_isGroupSystem
Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

namespace ProCGroups.InverseSystems
universe u v
variable {I : Type u} [Preorder I] (S : InverseSystem.{u, v} (I := I))
  [∀ i, Group (S.X i)] [IsGroupSystem S]
instance InverseSystem.restrict_isGroupSystem (J : Set I) :
    IsGroupSystem (S.restrict J) where
  map_one := fun {_ _} h => IsGroupSystem.map_one (S := S) h
  map_mul := fun {_ _} h x y => IsGroupSystem.map_mul (S := S) h x y
  map_inv := fun {_ _} h x => IsGroupSystem.map_inv (S := S) h x