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Small fix
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aisejohan committed May 14, 2024
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Showing 1 changed file with 9 additions and 5 deletions.
14 changes: 9 additions & 5 deletions algebra.tex
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Expand Up @@ -15336,11 +15336,15 @@ \section{Associated primes}
\end{lemma}

\begin{proof}
The first equality follows, since if $m \in S^{-1}M$, then the annihilator
of $m$ in $R$ is the intersection of the annihilator of $m$ in $S^{-1}R$
with $R$.
The displayed inclusion and equality in the Noetherian case follows from
Lemma \ref{lemma-associated-primes-localize}
For $m \in S^{-1}M$, let $I \subset R$ and $J \subset S^{-1}R$ be the
annihilators of $m$. Then $I$ is the inverse image of $J$ by the map
$R \to S^{-1}R$ and $J = S^{-1}I$. The equality in (1) follows by the
description of the map $\Spec(S^{-1}R) \to \Spec(R)$ in
Lemma \ref{lemma-spec-localization}.
For $m \in M$, let $I \subset R$ be the annihilator of $m$ in $R$
and let $J \subset S^{-1}R$ be the annihilator of $m/1 \in S^{-1}M$.
We have $J = S^{-1}I$ which implies (2). The equality in the
Noetherian case follows from Lemma \ref{lemma-associated-primes-localize}
since for $\mathfrak p \in R$, $S \cap \mathfrak p = \emptyset$ we have
$M_{\mathfrak p} = (S^{-1}M)_{S^{-1}\mathfrak p}$.
\end{proof}
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