Graded Local Cohomology: Attached and Associated Primes, Asymptotic Behaviors

Mohammad T. Dibaei, Alireza Nazari

Published 2006-01-25, updated 2006-04-19Version 2

Assume that $R = \bigoplus_{i\in \mathbb{N}_{0}} R_{i}$ is a homogeneous graded Noetherian ring, and that $M$ is a $ \mathbb{Z}$--graded $R$--module, where $ \mathbb{N}_{0}$ (resp. $ \mathbb{Z}$) denote the set all non--negative integers (resp. integers). The set of all homogeneous attached prime ideals of the top non--vanishing local cohomology module of a finitely generated module $M$, $\LH_{R_{+}}^{c}(M)$, with respect to the irrelevant ideal $R_{+}: =\bigoplus_{i\geq 1} R_{i}$ and the set of associated primes of $\LH _{R_{+}}^{i}(M)$ is studied. The asymptotic behavior of $\Hom_{R}(R/R_{+}, \LH _{R_{+}}^{s}(M))$ for $s \geq f(M)$ is discussed, where $f(M)$ is the finiteness dimension of $M$. It is shown that $\LH_{R_{+}}^{h}(M)$ is tame if $\LH_{R_{+}}^{i}(M)$ is Artinian for all $i > h$.