diff --git a/chow.tex b/chow.tex index 26d20627a..da9c9754e 100644 --- a/chow.tex +++ b/chow.tex @@ -3545,7 +3545,8 @@ \section{Proper pushforward} \end{enumerate} Note that the statement makes sense since $f_*\mathcal{F}$ and $f_*\mathcal{O}_Z$ are coherent $\mathcal{O}_Y$-modules by -Cohomology of Schemes, Lemma \ref{coherent-lemma-proper-pushforward-coherent}. +Cohomology of Schemes, Proposition +\ref{coherent-proposition-proper-pushforward-coherent}. \end{lemma} \begin{proof} diff --git a/coherent.tex b/coherent.tex index 55a5f2330..b8afc074d 100644 --- a/coherent.tex +++ b/coherent.tex @@ -3802,14 +3802,14 @@ \section{Higher direct images of coherent sheaves} \noindent Here is the general statement. -\begin{lemma} -\label{lemma-proper-pushforward-coherent} +\begin{proposition} +\label{proposition-proper-pushforward-coherent} Let $S$ be a locally Noetherian scheme. Let $f : X \to S$ be a proper morphism. Let $\mathcal{F}$ be a coherent $\mathcal{O}_X$-module. Then $R^if_*\mathcal{F}$ is a coherent $\mathcal{O}_S$-module for all $i \geq 0$. -\end{lemma} +\end{proposition} \begin{proof} Since the problem is local on $S$ we may assume that $S$ is @@ -3883,10 +3883,10 @@ \section{Higher direct images of coherent sheaves} as in the statement of Chow's lemma. Also, let $U \subset Z$ be the dense open subscheme such that $\pi^{-1}(U) \to U$ is an isomorphism. By the discussion in Remark \ref{remark-chow-Noetherian} we see that -$i' = (i, \pi) : \mathbf{P}^n_S \times_S Z' = \mathbf{P}^n_Z$ is +$i' = (i, \pi) : Z' \to \mathbf{P}^n_Z$ is a closed immersion. Hence $$ -\mathcal{L} = i^*\mathcal{O}_{\mathbf{P}^n_X}(1) \cong +\mathcal{L} = i^*\mathcal{O}_{\mathbf{P}^n_S}(1) \cong (i')^*\mathcal{O}_{\mathbf{P}^n_Z}(1) $$ is $g'$-relatively ample and $\pi$-relatively ample (for example by @@ -3932,8 +3932,8 @@ \section{Higher direct images of coherent sheaves} $\mathcal{F} = i_*\mathcal{G}$ for some coherent module $\mathcal{G}$ on $Z$ (Lemma \ref{lemma-coherent-support-closed}). Denoting $g : Z \to S$ the composition $f \circ i$ we see that -$R^pg_*\mathcal{G}$ -is coherent on $S$ by Lemma \ref{lemma-proper-pushforward-coherent}. +$R^pg_*\mathcal{G}$ is coherent on $S$ by +Proposition \ref{proposition-proper-pushforward-coherent}. On the other hand, $R^qi_*\mathcal{G} = 0$ for $q > 0$ (Lemma \ref{lemma-finite-pushforward-coherent}). By Cohomology, Lemma \ref{cohomology-lemma-relative-Leray} @@ -3950,7 +3950,8 @@ \section{Higher direct images of coherent sheaves} \end{lemma} \begin{proof} -This is just the affine case of Lemma \ref{lemma-proper-pushforward-coherent}. +This is just the affine case of +Proposition \ref{proposition-proper-pushforward-coherent}. Namely, by Lemmas \ref{lemma-quasi-coherence-higher-direct-images} and \ref{lemma-quasi-coherence-higher-direct-images-application} we know that $R^if_*\mathcal{F}$ is the quasi-coherent sheaf associated @@ -4488,7 +4489,7 @@ \section{The theorem on formal functions} $p > 0$. Hence we see that $(R^pf_*\mathcal{F})_y^\wedge = 0$ by Lemma \ref{lemma-formal-functions-stalk}. Note that $R^pf_*\mathcal{F}$ is coherent by -Lemma \ref{lemma-proper-pushforward-coherent} and +Proposition \ref{proposition-proper-pushforward-coherent} and hence $R^pf_*\mathcal{F}_y$ is a finite $\mathcal{O}_{Y, y}$-module. By Algebra, Lemma \ref{algebra-lemma-completion-tensor} @@ -4518,11 +4519,11 @@ \section{The theorem on formal functions} Moreover, the underlying topological space of each infinitesimal neighbourhood $X_n$ is the same as that of $X_y$. Hence $H^p(X_n, \mathcal{F}_n) = 0$ for all $p > d$ by -Cohomology, Lemma \ref{cohomology-lemma-vanishing-Noetherian}. +Cohomology, Proposition \ref{cohomology-proposition-vanishing-Noetherian}. Hence we see that $(R^pf_*\mathcal{F})_y^\wedge = 0$ by Lemma \ref{lemma-formal-functions-stalk} for $p > d$. Note that $R^pf_*\mathcal{F}$ is coherent by -Lemma \ref{lemma-proper-pushforward-coherent} and +Proposition \ref{proposition-proper-pushforward-coherent} and hence $R^pf_*\mathcal{F}_y$ is a finite $\mathcal{O}_{Y, y}$-module. By Algebra, Lemma \ref{algebra-lemma-completion-tensor} @@ -5363,7 +5364,7 @@ \section{Grothendieck's existence theorem, II} \begin{proof} Since $f$ is a proper morphism we see that $f_*\mathcal{F}$ is a coherent $\mathcal{O}_Y$-module -(Lemma \ref{lemma-proper-pushforward-coherent}). +(Proposition \ref{proposition-proper-pushforward-coherent}). Thus the statement of the lemma makes sense. Consider the compositions $$ @@ -5503,7 +5504,7 @@ \section{Grothendieck's existence theorem, II} (Lemma \ref{lemma-existence-projective}) there exists a coherent module $\mathcal{F}'$ on $X'$ such that $(\mathcal{F}')^\wedge \cong (f^*\mathcal{F}_n)$. By -Lemma \ref{lemma-proper-pushforward-coherent} +Proposition \ref{proposition-proper-pushforward-coherent} the $\mathcal{O}_X$-module $\mathcal{H} = f_*\mathcal{F}'$ is coherent and by Lemma \ref{lemma-inverse-systems-push-pull} there exists a morphism $(\mathcal{F}_n) \to \mathcal{H}^\wedge$ @@ -5634,9 +5635,8 @@ \section{Grothendieck's existence theorem, II} \medskip\noindent Let $\mathcal{K}$ be the quasi-coherent sheaf of ideals cutting -out the reduced complement $X \setminus U$. -By -Lemma \ref{lemma-proper-pushforward-coherent} +out the reduced complement $X \setminus U$. By +Proposition \ref{proposition-proper-pushforward-coherent} the $\mathcal{O}_X$-module $\mathcal{H} = f_*\mathcal{F}'$ is coherent and by Lemma \ref{lemma-inverse-systems-push-pull} there exists a morphism $\alpha : (\mathcal{F}_n) \to \mathcal{H}^\wedge$ diff --git a/cohomology.tex b/cohomology.tex index 2f04aed47..cb1191160 100644 --- a/cohomology.tex +++ b/cohomology.tex @@ -3172,7 +3172,7 @@ \section{Vanishing on Noetherian topological spaces} \noindent The aim is to prove a theorem of Grothendieck namely -Lemma \ref{lemma-vanishing-Noetherian}. See \cite{Tohoku}. +Proposition \ref{proposition-vanishing-Noetherian}. See \cite{Tohoku}. \begin{lemma} \label{lemma-cohomology-and-closed-immersions} @@ -3397,8 +3397,8 @@ \section{Vanishing on Noetherian topological spaces} hence we get the lemma. \end{proof} -\begin{lemma} -\label{lemma-vanishing-Noetherian} +\begin{proposition}[Grothendieck] +\label{proposition-vanishing-Noetherian} \begin{reference} \cite[Theorem 3.6.5]{Tohoku}. \end{reference} @@ -3406,7 +3406,7 @@ \section{Vanishing on Noetherian topological spaces} If $\dim(X) \leq d$, then $H^p(X, \mathcal{F}) = 0$ for all $p > d$ and any abelian sheaf $\mathcal{F}$ on $X$. -\end{lemma} +\end{proposition} \begin{proof} We prove this lemma by induction on $d$. @@ -3659,7 +3659,8 @@ \section{Cohomology on spectral spaces} \noindent The following result on cohomological vanishing -improves Grothendieck's result (Lemma \ref{lemma-vanishing-Noetherian}) +improves Grothendieck's result +(Proposition \ref{proposition-vanishing-Noetherian}) and can be found in \cite{Scheiderer}. \begin{proposition} diff --git a/crystalline.tex b/crystalline.tex index e29ff208a..62ec4358c 100644 --- a/crystalline.tex +++ b/crystalline.tex @@ -4698,7 +4698,8 @@ \section{Some further results} of dimension $e$ over $S$ (see Lemma \ref{lemma-compute-cohomology-crystal-smooth}). These de Rham complexes are zero in all degrees $>e$. Hence (1) -follows from Cohomology, Lemma \ref{cohomology-lemma-vanishing-Noetherian}. +follows from Cohomology, Proposition +\ref{cohomology-proposition-vanishing-Noetherian}. In case (2) we use the alternating {\v C}ech complex (see Remark \ref{remark-alternating-cech-complex}) to reduce to the case $X$ affine. In the affine case we prove the result using the de Rham complex diff --git a/etale-cohomology.tex b/etale-cohomology.tex index fc910982e..bedc6ce61 100644 --- a/etale-cohomology.tex +++ b/etale-cohomology.tex @@ -7551,9 +7551,7 @@ \section{Vanishing of finite higher direct images} Algebra, Lemma \ref{algebra-lemma-ring-with-only-minimal-primes}. Thus the higher cohomology groups of an abelian sheaf on the topological space $S$ (i.e., Zariski cohomology) is trivial, see -Topology, Lemma \ref{topology-lemma-profinite-refine-open-covering} -and -Cohomology on Sites, Lemma \ref{sites-cohomology-lemma-w-contractible}. +Cohomology, Lemma \ref{cohomology-lemma-vanishing-for-profinite}. The local rings are strictly henselian by Algebra, Lemma \ref{algebra-lemma-local-dimension-zero-henselian}. Thus \'etale cohomology of $S$ is computed by Zariski cohomology @@ -8930,7 +8928,8 @@ \section{The Artin-Schreier sequence} be a coherent sheaf of ideals on $Z$. To finish the proof have to show that $H^d(X, i_*\mathcal{I}) = H^d(Z, \mathcal{I})$ is finite dimensional. If $\dim(Z) < d$, then the result holds because the cohomology group -will be zero (Cohomology, Lemma \ref{cohomology-lemma-vanishing-Noetherian}). +will be zero (Cohomology, Proposition +\ref{cohomology-proposition-vanishing-Noetherian}). In this way we reduce to the situation discussed in the following paragraph. \medskip\noindent diff --git a/more-morphisms.tex b/more-morphisms.tex index 9d1dacc04..ece8558f9 100644 --- a/more-morphisms.tex +++ b/more-morphisms.tex @@ -9350,7 +9350,8 @@ \section{Stein factorization} and finite type (Morphisms, Lemma \ref{morphisms-lemma-permanence-finite-type}). Hence $f'$ is proper. By -Cohomology of Schemes, Lemma \ref{coherent-lemma-proper-pushforward-coherent} +Cohomology of Schemes, Proposition +\ref{coherent-proposition-proper-pushforward-coherent} we see that $f_*\mathcal{O}_X$ is a coherent $\mathcal{O}_S$-module. Hence we see that $\pi$ is finite, i.e., (2) holds. diff --git a/perfect.tex b/perfect.tex index 7a40ec85b..a64cf8aac 100644 --- a/perfect.tex +++ b/perfect.tex @@ -2623,7 +2623,7 @@ \section{Compact and perfect objects} \noindent Let $X$ be a Noetherian scheme of finite dimension. By -Cohomology, Lemma \ref{cohomology-lemma-vanishing-Noetherian} +Cohomology, Proposition \ref{cohomology-proposition-vanishing-Noetherian} and Cohomology on Sites, Lemma \ref{sites-cohomology-lemma-when-jshriek-compact} the sheaves of modules $j_!\mathcal{O}_U$ are compact objects diff --git a/tags/tags b/tags/tags index 112f19591..23359a3da 100644 --- a/tags/tags +++ b/tags/tags @@ -3499,7 +3499,7 @@ 02O2,coherent-section-chows-lemma 02O3,coherent-section-proper-pushforward 02O4,coherent-lemma-locally-projective-pushforward -02O5,coherent-lemma-proper-pushforward-coherent +02O5,coherent-proposition-proper-pushforward-coherent 02O6,coherent-lemma-proper-over-affine-cohomology-finite 02O7,coherent-section-theorem-formal-functions 02O8,coherent-lemma-cohomology-powers-ideal-times-F @@ -3745,7 +3745,7 @@ 02UW,cohomology-lemma-irreducible-constant-cohomology-zero 02UX,cohomology-lemma-vanishing-generated-one-section 02UY,cohomology-lemma-subsheaf-irreducible -02UZ,cohomology-lemma-vanishing-Noetherian +02UZ,cohomology-proposition-vanishing-Noetherian 02V0,schemes-lemma-composition-immersion 02V1,morphisms-lemma-composition-universally-injective 02V2,morphisms-lemma-composition-open diff --git a/varieties.tex b/varieties.tex index a476fcfae..3ee9c06cc 100644 --- a/varieties.tex +++ b/varieties.tex @@ -2631,8 +2631,8 @@ \section{Types of varieties} \end{lemma} \begin{proof} -By -Cohomology of Schemes, Lemma \ref{coherent-lemma-proper-pushforward-coherent} +By Cohomology of Schemes, Proposition +\ref{coherent-proposition-proper-pushforward-coherent} we see that $\Gamma(X, \mathcal{O}_X)$ is a finite dimensional $k$-vector space. It is also a $k$-algebra without zero-divisors. Hence it is a field, see @@ -4351,7 +4351,7 @@ \section{One dimensional Noetherian schemes} $$ of sheaves of abelian groups on $X$. Since $\dim(X) \leq 1$ we see that $H^2(X, \mathcal{F}) = 0$ for any abelian sheaf $\mathcal{F}$, see -Cohomology, Lemma \ref{cohomology-lemma-vanishing-Noetherian}. +Cohomology, Proposition \ref{cohomology-proposition-vanishing-Noetherian}. Hence the map $H^1(X, \mathcal{O}^*_X) \to H^1(Z, \mathcal{O}_Z^*)$ is surjective. This proves the lemma by Cohomology, Lemma \ref{cohomology-lemma-h1-invertible}.