When are the Rees algebras of parameter ideals almost Gorenstein graded rings?

Abstract

Let A be a Cohen–Macaulay local ring with dimA=d≥3, possessing the canonical module KA. Let a1,a2,…,ar (3≤r≤d) be a subsystem of parameters of A, and set Q=(a1,a2,…,ar). We show that if the Rees algebra R(Q) of Q is an almost Gorenstein graded ring, then A is a regular local ring and a1,a2,…,ar is a part of a regular system of parameters of A.