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Trivial but interesting combination of results
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aisejohan committed Jan 16, 2018
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Expand Up @@ -5562,6 +5562,37 @@ \section{Algebraization of local cohomology, bootstrap}
The result follows easily from Lemma \ref{lemma-bootstrap}.
\end{proof}

\begin{remark}
\label{remark-combine}
Let $I \subset \mathfrak a \subset A$ be ideals of a Noetherian ring $A$
and let $M$ be a finite $A$-module. Let $s$ and $d$ be integers.
Suppose that
\begin{enumerate}
\item $A, I, \mathfrak a, M$ satisfy the conditions of
Situation \ref{situation-bootstrap} for $s$ and $d$, and
\item $A, I, \mathfrak a, M$ satisfy the conditions of
Lemma \ref{lemma-algebraize-local-cohomology-general}
for $s + 1$ and $d$ with $J = \mathfrak a$.
\end{enumerate}
Then there exists an ideal
$J_0 \subset \mathfrak a$ with $V(J_0) \cap V(I) = V(\mathfrak a)$
such that for any $J' \subset J_0$ with $V(J') \cap V(I) = V(\mathfrak a)$
the map
$$
H^{s + 1}_{J'}(M) \longrightarrow \lim H^{s + 1}_\mathfrak a(M/I^nM)
$$
is an isomorphism. Namely, we have the existence of $J_0$
and the isomorphism
$H^{s + 1}_{J'}(M) = H^{s + 1}(R\Gamma_\mathfrak a(M)^\wedge)$
by Lemma \ref{lemma-algebraize-local-cohomology-general},
we have $H^{s + 1}(R\Gamma_\mathfrak a(M)^\wedge)$ sandwiched
between the limit and $R^1\lim H^s_\mathfrak a(M/I^nM)$ by
Dualizing Complexes, Lemma \ref{dualizing-lemma-completion-local},
and we have the vanishing of
$R^1\lim H^s_\mathfrak a(M/I^nM)$ by Lemma \ref{lemma-final-bootstrap}.
\end{remark}





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