Category of Profinite Groups #
We say G is a profinite group if it is a topological group which is compact and totally
disconnected.
Main definitions and results #
ProfiniteGrpis the category of profinite groups.ProfiniteGrp.pi: The pi-type of profinite groups is also a profinite group.ofFiniteGrp: AFiniteGrpwhen given the discrete topology can be considered as a profinite group.ofClosedSubgroup: A closed subgroup of a profinite group is profinite.
The category of profinite groups. A term of this type consists of a profinite set with a topological group structure.
- toProfinite : Profinite
The underlying profinite topological space.
- group : Group ↑self.toProfinite.toTop
The group structure.
- topologicalGroup : IsTopologicalGroup ↑self.toProfinite.toTop
The above data together form a topological group.
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The category of profinite additive groups. A term of this type consists of a profinite set with a topological additive group structure.
- toProfinite : Profinite
The underlying profinite topological space.
- addGroup : AddGroup ↑self.toProfinite.toTop
The additive group structure.
- topologicalAddGroup : IsTopologicalAddGroup ↑self.toProfinite.toTop
The above data together form a topological additive group.
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Construct a term of ProfiniteGrp from a type endowed with the structure of a
compact and totally disconnected topological group.
(The condition of being Hausdorff can be omitted here because totally disconnected implies that {1}
is a closed set, thus implying Hausdorff in a topological group.)
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Construct a term of ProfiniteAddGrp from a type endowed with the structure of a
compact and totally disconnected topological additive group.
(The condition of being Hausdorff can be omitted here because totally disconnected implies that {0}
is a closed set, thus implying Hausdorff in a topological additive group.)
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The underlying ContinuousMonoidHom.
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The underlying ContinuousAddMonoidHom.
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Typecheck a ContinuousMonoidHom as a morphism in ProfiniteGrp.
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Typecheck a ContinuousAddMonoidHom as a morphism in ProfiniteAddGrp.
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Construct a term of ProfiniteGrp from a type endowed with the structure of a
profinite topological group.
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Construct a term of ProfiniteAddGrp from a type endowed with the structure of a
profinite topological additive group.
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The pi-type of profinite groups is a profinite group.
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The pi-type of profinite additive groups is a profinite additive group.
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A FiniteGrp when given the discrete topology can be considered as a profinite group.
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A FiniteAddGrp when given the discrete topology can be considered as a
profinite additive group.
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A morphism of FiniteGrp induces a morphism of the associated profinite groups.
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A morphism of FiniteAddGrp induces a morphism of the associated profinite
additive groups.
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A closed subgroup of a profinite group is profinite.
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A closed additive subgroup of a profinite additive group is profinite.
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A topological group that has a ContinuousMulEquiv to a profinite group is profinite.
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A topological additive group that has a ContinuousAddEquiv to a
profinite additive group is profinite.
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Build an isomorphism in the category ProfiniteGrp from
a ContinuousMulEquiv between ProfiniteGrps.
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The functor mapping a profinite group to its underlying profinite space.
Limits in the category of profinite groups #
In this section, we construct limits in the category of profinite groups.
ProfiniteGrp.limitCone: The explicit limit cone inProfiniteGrp.ProfiniteGrp.limitConeIsLimit:ProfiniteGrp.limitConeis a limit cone.
Auxiliary construction to obtain the group structure on the limit of profinite groups.
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Auxiliary construction to obtain the additive group structure on the limit of profinite additive groups.
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The explicit limit cone in ProfiniteGrp.
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The explicit limit cone in ProfiniteAddGrp.
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ProfiniteGrp.limitCone is a limit cone.
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ProfiniteAddGrp.limitCone is a limit cone.
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The abbreviation for the limit of ProfiniteGrps.
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The abbreviation for the limit of ProfiniteAddGrps.