Annihilator of Top Local Cohomology and Lynch's Conjecture

Abstract

Let $R$ be a commutative Noetherian ring, $\mathfrak a$ a proper ideal of $R$ and $N$ a non-zero finitely generated $R$-module with $N\neq \mathfrak a N$. Let $d$ (respectively $c$) be the smallest (respectively greatest) non-negative integer $i$ such that the local cohomology $\operatorname{H}^i_{\mathfrak a}(N)$ is non-zero. In this paper, we provide sharp bounds under inclusion for the annihilators of the local cohomology modules $\operatorname{H}^d_{\mathfrak a}(N)$, $\operatorname{H}^c_{\mathfrak a}(N)$ and these annihilators are computed in certain cases. Also, we construct a counterexample to Lynch's conjecture.