Talk:Residually finite

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Mathematics grading: Stub Class Importance unassessed.  Field: Algebra

[edit] Unsourced (nontrivial?) theorem

An equivalent definition is that a group is residually finite if the intersection of all its finite index subgroups is trivial.

Er, really? Without thinking about this, at all, it is quite obvious that a group is RF if the intersection of all its finite index normal subgroups is trivial. Can someone provide a proof for the other equivalence?

RandomP 14:45, 22 September 2006 (UTC)

Probably an error? I changed it to "normal", which generally occurs in the definition of "residually something". - Momotaro 14:00, 21 February 2007 (UTC)
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