Asymptotic depth of twisted higher direct image sheaves

Author:

Bär Renate,Brodmann Markus

Abstract

Let π : X X 0 \pi :X \rightarrow X_{0} be a projective morphism of schemes, such that X 0 X_{0} is Noetherian and essentially of finite type over a field K K . Let i N 0 i \in \mathbb {N}_{0} , let F {\mathcal {F}} be a coherent sheaf of O X {\mathcal {O}}_{X} -modules and let L {\mathcal {L}} be an ample invertible sheaf over X X . Let Z 0 X 0 Z_{0} \subseteq X_{0} be a closed set. We show that the depth of the higher direct image sheaf R i π ( L n O X F ) {\mathcal {R}}^{i}\pi _{*}({\mathcal {L}}^{n} \otimes _{{\mathcal {O}}_{X}} {\mathcal {F}}) along Z 0 Z_{0} ultimately becomes constant as n n tends to -\infty , provided X 0 X_{0} has dimension 2 \leq 2 . There are various examples which show that the mentioned asymptotic stability may fail if dim ( X 0 ) 3 \dim (X_{0}) \geq 3 . To prove our stability result, we show that for a finitely generated graded module M M over a homogeneous Noetherian ring R = n 0 R n R=\bigoplus _{n \geq 0}R_{n} for which R 0 R_{0} is essentially of finite type over a field and an ideal a 0 R 0 \mathfrak {a}_{0} \subseteq R_{0} , the a 0 \mathfrak {a}_{0} -depth of the n n -th graded component H R + i ( M ) n H^{i}_{R_{+}}(M)_{n} of the i i -th local cohomology module of M M with respect to R + := k > 0 R k R_{+}:=\bigoplus _{k>0}R_{k} ultimately becomes constant in codimension 2 \leq 2 as n n tends to -\infty .

Publisher

American Mathematical Society (AMS)

Subject

Applied Mathematics,General Mathematics

Reference8 articles.

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Cited by 1 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Analytic spread and non-vanishing of asymptotic depth;Mathematical Proceedings of the Cambridge Philosophical Society;2017-03-08

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