Let $A$ be a commutative ring, $S\subseteq A$ closed under multiplication, and consider $S^{-1}A$ the localization of $A$ in $S$. Let $M$ be an $S^{-1}A$-module. Does it necessarily exist an $A$-module $M'$ such that $M = S^{-1}M'$?
Im trying to prove that if $M$ is projective, then its localization at $S$ is an $S^{-1}A$ projective module. In this question I'm not looking for the solution to this problem, but an answer to what I'm asking. I simply add this information for contextualization!
Thanks in advance!
An $S^{-1}A$-module $M$ is also an $A$-module (via the ring homomorphism $A\to S^{-1}A$). Then $S^{-1}M=M$, or strictly speaking the localisation of the $A$-module $M$ is naturally isomorphic to the $S^{-1}A$-module $M$.