Integral closure and local cohomology

Abstract

Let $A$ be a Noetherian ring and let $I$ be an ideal in $A$. Let $\mathcal{F} = \{ J_n \}_{n \geq 0}$ be a multiplicative filtration of ideals in $A$ such that $\mathcal{R}(\mathcal{F}) = \bigoplus_{n \geq 0} J_n$ is a finitely generated $A$-algebra. Let $\mathcal{R} = A[It]$ and assume $I^n \subseteq J_n$ for all $n \geq 1$. We show the following two assertions are equivalent: (1) For all $i \geq 0$ we have $H^i_{\mathcal{R}_+}(\mathcal{R}(\mathcal{F}))_n = 0$ for all $n \gg 0$. (2) $J_n \subseteq \overline{I^n}$ for all $n \geq 1$. Here $\overline{I^n}$ is the integral closure of $I^n$.