Some Results about Endomorphism Rings for Local Cohomology Defined by a Pair of Ideals

TL;DR

This paper extends the Local Duality Theorem to local cohomology defined by pairs of ideals and investigates the structure of endomorphism rings of these cohomology modules in Cohen-Macaulay rings.

Contribution

It generalizes the Local Duality Theorem for local cohomology with respect to pairs of ideals and analyzes endomorphism rings in Cohen-Macaulay settings.

Findings

Generalized Local Duality Theorem for pairs of ideals

Isomorphism of endomorphism rings in Cohen-Macaulay rings

Behavior of endomorphism rings of local cohomology modules

Abstract

Let $(R,\mathfrak{m},k)$ denote a local ring. For $I$ and $J$ ideals of $R$, for all integer $i$, let $H^i_{I,J}(-)$ denote the $i$-th local cohomology functor with respect to $(I,J)$. Here we give a generalized version of Local Duality Theorem for local cohomology defined by a pair of ideals. Also, for $M$ be a finitely generated $R$-module, we study the behavior of the endomorphism rings $H^t_{I,J}(M)$ and $D(H^t_{I,J}(M))$ where $t$ is the smallest integer such that the local cohomology with respect to a pair of ideals is non-zero and $D(-):= {\rm Hom}_R(-,E_R(k))$ is the Matlis dual functor. We show too that if $R$ be a $d$-dimensional complete Cohen-Macaulay and $H^i_{I,J}(R)=0$ for all $i\neq t$, the natural homomorphism $R\rightarrow {\rm Hom}_R(H^t_{I,J}(K_R), H^t_{I,J}(K_R))$ is an isomorphism and for all $i\neq t$, where $K_R$ denote the canonical module of $R$.