I am reading Edwin Wiess' book called Cohomology of groups and I cant see why the following claim he makes is true in proposition 3-1-9.
He says that if $A$ is a finitely generated $G$-module for a finite group $G$ where $|G|=m$, that $A/mA$ is finite, where m is the multiplication by m map.
How does he know its finite? is this a standard result?
Thank you
Do you know that a f.g. abelian torsion group is finite? Well, that's precisely what $\,A/mA\,$ is: a f.g. abelian torsion group generated, as a $\,G\,$ module (and this usually means $\,A\,$ is a f.g. $\,\Bbb Z[G]-$module. Check this), by the images of a $\,G-$generator set in the quotient $\,A/mA\,$