On Tor-vanishing of local rings

Abstract: Let $R$ be a local ring with residue field $k$ and $M$, $N$ be finitely generated modules over $R$. It is well known that $Tor^R_i(M, N) = 0$ for $i \gg 0$ if $pd_R(M) < \infty$ or $pd_R(N) < \infty$. The ring $R$ is said to satisfy the Tor-vanishing property if the converse holds, that is, $Tor^R_i(M, N) = 0$ for $i \gg 0$ implies $pd_R(M) < \infty$ or $pd_R(N) < \infty$. Interest in the Tor-vanishing property stems from the fact that Cohen-Macaulay local rings satisfying this property also satisfy the Auslander-Reiten conjecture. In this article, we study a variant of this property. If $R$ is a generalized Golod ring, we prove that $Tor^R_i(M, N) = 0$ for $i \gg 0$ implies ${curv_R M, curv_R N } \cap {0, 1} \neq \emptyset$. A key intermediate step in our proof is to show that $curv_R M \in {0, 1, curv_R k}$ for any module $M$ over a generalized Golod ring $R$. As an application, we prove that generic Gorenstein local rings, non-trivial connected sums of generalized Golod-Gorenstein rings satisfy the Tor-vanishing property and consequently the Auslander-Reiten conjecture. Our method suggests a uniform approach and recovers many old results on the Tor-vanishing property.