We can define two topologies on a group $G$ by considering all normal subgroups of finite index (resp. of index a finite power of $p$ - where $p$ is a prime) as basis of $1\in G$.
My questions: Under what conditions these two topologies coincide? What are the usual approaches to check whether they coincide in a given f.g. group?
To coincide is equivalent to the following. For each normal subgroup $N$ of finite index, there exists a normal subgroup $P$ of index a finite power of $p$ such that $P\subseteq N$.
So, a trivial situation is when each finite quotient of $G$ is a $p$-group.
Thanks in advance for any ideas! Explicit examples are very welcome too.
