A pro- group, for a fixed prime
, is a topological group
isomorphic to an inverse limit of finite
-groups. It is a profinite
group whose continuous finite quotient groups all
have order a power of
.
The additive group
is an example. For a profinite
group
,
its maximal pro-
quotient is the quotient through which every continuous homomorphism from
to a pro-
group factors.
In the Bogomolov-Pop conjecture, a prime different from the field
characteristic is fixed and the maximal pro-
absolute Galois group
retains field information after further passage to its
abelian-by-central quotient.