arXiv subjects

Reza Naghipour

Publications and source records attributed to Reza Naghipour.

25 records · Page 2Linked to original sources

arXiv2013

Cofiniteness of local cohomology modules for ideals of dimension one

Let $R$ denote a commutative Noetherian (not necessarily local) ring, $M$ an arbitrary $R$-module and $I$ an ideal of $R$ of dimension one. It is shown that the $R$-module $\Ext^i_R(R/I,M)$ is finitely generated (resp. weakly Laskerian) for all $i\leq {\rm cd}(I,M)+1$ if and only if the local cohomology module $H^i_I(M)$ is $I$-cofinite (resp. $I$-weakly cofinite) for all $i$. Also, we show that when $I$ is an arbitrary ideal and $M$ is finitely generated module such that the $R$-module $H^i_I(M)$ is weakly Laskerian for all $i\leq t-1$, then $H^i_I(M)$ is $I$-cofinite for all $i\leq t-1$ and for any minimax submodule $K$ of $H^{t}_I(M)$, the $R$-modules $\Hom_R(R/I, H^{t}_I(M)/K)$ and $\Ext^{1}_R(R/I, H^{t}_I(M)/K)$ are finitely generated, where $t$ is a non-negative integer. This generalizes the main result of Bahmanpour-Naghipour \cite{BN} and Brodmann and Lashgari \cite{BL}.

math.AC↗

arXiv2013

Socle finiteness of local cohomology modules and Gorenstein ideals

The purpose of this paper is to give some equivalent conditions to the socle and Bass numbers' conjectures which raised by C. Huneke in (Problems on local cohomology, Free resolutions in commutative algebra and algebraic geometry, Res. Notes Math. 1992, pp. 93-108). In addition, some results about certain Gorenstein ideals are included.

math.AC↗

arXiv2013

A new characterization of Cohen-Macaulay rings

The purpose of this article is to provide a new characterization of Cohen-Macaulay local rings. As a consequence we deduce that a local (Noetherian) ring $R$ is Gorenstein if and only if every parameter ideal of $R$ is irreducible.

math.AC↗

arXiv2013

Quintasymptotic sequences over an ideal and quintasymptotic cograde

Let $I$ denote an ideal of a Noetherian ring $R$. The purpose of this article is to introduce the concepts of quintasymptotic sequences over $I$ and quintasymptotic cograde of $I$, and it is shown that they play a role analogous to quintessential sequences over $I$ and quintessential cograde of $I$, given in \cite{Ra1}. Also, we show that, if $R$ is local, then the quintasymptotic cograde of $I$ is unambiguously defined and behaves well when passing to certain related local rings. Finally, we use this cograde to characterize of two classes of local rings.

math.AC↗

arXiv2013

On the generalization of Faltings' Annihilator Theorem

Let $R$ be a commutative Noetherian ring and let $n$ be a non-negative integer. In this article, by using the theory of Gorenstein dimensions, it is shown that whenever $R$ is a homomorphic image of a Noetherian Gorenstein ring, then the invariants $\inf\{i\in\nat_0|\, {\dim\Supp}(\fb^tH_{\fa}^i(M))\geq n\text{for all} t\in\nat_0\}$ and $\inf\{λ_{\fa R_{\p}}^{\fb R_{\p}}(M_{\p})|\,\p\in {\rm Spec} \, R \text{and} \dim R/ \p\geq n\}$ are equal, for every finitely generated $R$-module $M$ and for every ideals $\frak a, \frak b$ of $R$ with $\frak b\subseteq \frak a$. This generalizes the Faltings' Annihilator Theorem [G. Faltings, {\it Über die Annulatoren lokaler Kohomologiegruppen}, Arch. Math. {\bf30} (1978) 473-476].

math.AC↗

arXiv2013

Faltings' local-global principle for the minimaxness of local cohomology modules

The concept of Faltings' local-global principle for the minimaxness of local cohomology modules over a commutative Noetherian ring $R$ is introduced, and it is shown that this principle holds at level 2. We also establish the same principle at all levels over an arbitrary commutative Noetherian ring of dimension not exceeding 3. These generalize the main results of Brodmann et al. in \cite{BRS}. Moreover, it is shown that if $M$ is a finitely generated $R$-module, $\frak a$ an ideal of $R$ and $r$ a non-negative integer such that $\frak a^tH^i_{\frak a}(M)$ is skinny for all $i<r$ and for some positive integer $t$, then for any minimax submodule $N$ of $H^r_{\frak a}(M)$, the $R$-module $\Hom_R(R/\frak a, H^r_{\frak a}(M)/N)$ is finitely generated. As a consequence, it follows that the associated primes of $H^r_{\frak a}(M)/N$ are finite. This generalizes the main results of Brodmann-Lashgari \cite{BL} and Quy \cite{Qu}.

math.AC↗

arXiv2013

Faltings' local-global principle for the finiteness of local cohomology modules

Let (R,m) be a complete local ring, a an ideal of R and M a finitely generated R-module. The aim of this paper is to show that for any non-negative integer n, the least integer i such that the i-th local cohomology with respect to a is not in dimension <n, is equal to the n-th finiteness dimension of M relative to a. This generalizes the main result of Quy and Brodmann-Lashgari.

math.AC↗