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Compatibilities in spaces-dualizing
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There are infinitely many of these
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aisejohan committed Jul 14, 2017
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Expand Up @@ -2045,6 +2045,79 @@ \section{Relative dualizing complexes for proper flat morphisms}
and the proof is complete.
\end{proof}

\begin{lemma}
\label{lemma-base-change-relative-dualizing}
Let $S$ be a scheme. Consider a cartesian square
$$
\xymatrix{
X' \ar[d]_{f'} \ar[r]_{g'} & X \ar[d]^f \\
Y' \ar[r]^g & Y
}
$$
of algebraic spaces over $S$. Assume $X \to Y$ is proper, flat, and
of finite presentation. Let $(\omega_{X/Y}^\bullet, \tau)$ be a
relative dualizing complex for $f$. Then
$(L(g')^*\omega_{X/Y}^\bullet, Lg^*\tau)$ is a relative dualizing
complex for $f'$.
\end{lemma}

\begin{proof}
Observe that $L(g')^*\omega_{X/Y}^\bullet$ is $Y'$-perfect by
More on Morphisms of Spaces, Lemma
\ref{spaces-more-morphisms-lemma-base-change-relatively-perfect}.
The other condition of
Definition \ref{definition-relative-dualizing-proper-flat}
holds by transitivity of fibre products.
\end{proof}







\section{Comparison with the case of schemes}
\label{section-comparison}

\noindent
We should add a lot more in this section.

\begin{lemma}
\label{lemma-compare}
Let $S$ be a scheme. Let $f : X \to Y$ be a morphism of
quasi-compact and quasi-separated algebraic spaces over $S$.
Assume $X$ and $Y$ are representable and let $f_0 : X_0 \to Y_0$ be a
morphism of schemes representing $f$ (awkward but temporary notation).
Let $a : D_\QCoh(\mathcal{O}_Y) \to D_\QCoh(\mathcal{O}_X)$
be the right adjoint of $Rf_*$ from Lemma \ref{lemma-twisted-inverse-image}.
Let $a_0 : D_\QCoh(\mathcal{O}_{Y_0}) \to D_\QCoh(\mathcal{O}_{X_0})$
be the right adjoint of $Rf_*$ from
Duality for Schemes, Lemma \ref{duality-lemma-twisted-inverse-image}.
Then
$$
\xymatrix{
D_\QCoh(\mathcal{O}_{X_0})
\ar@{=}[rrrrrr]_{\text{Derived Categories of Spaces, Lemma
\ref{spaces-perfect-lemma-derived-quasi-coherent-small-etale-site}}}
& & & & & &
D_\QCoh(\mathcal{O}_X) \\
D_\QCoh(\mathcal{O}_{Y_0}) \ar[u]^{a_0}
\ar@{=}[rrrrrr]^{\text{Derived Categories of Spaces, Lemma
\ref{spaces-perfect-lemma-derived-quasi-coherent-small-etale-site}}}
& & & & & &
D_\QCoh(\mathcal{O}_Y) \ar[u]_a
}
$$
is commutative.
\end{lemma}

\begin{proof}
Follows from uniqueness of adjoints and the compatibilities of
Derived Categories of Spaces, Remark
\ref{spaces-perfect-remark-match-total-direct-images}.
\end{proof}





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