
Let \(R\) be a commutative noetherian ring, \(\mathfrak{a}\) an ideal of \(R\), and \(M\) and \(N\) two \(R\)-modules. Herzog defined the \(i\)th generalized local cohomology module of \(M\) and \(N\) with respect to \(\mathfrak{a}\) as follows: \[H^{i}_{\mathfrak{a}}(M,N) = \underset{n\in \mathbb{N}}\varinjlim \operatorname{Ext}^{i}_{R}(M/\mathfrak{a}^{n}M,N)\] On the other hand, \textit{R. Hartshorne} [Invent. Math. 9, 145--164 (1970; Zbl 0196.24301)] defined \(M\) to be \(\mathfrak{a}\)-cofinite if \(\operatorname{Supp}_{R}(M) \subseteq V(\mathfrak{a})\) and \(\operatorname{Ext}^{i}_{R}(R/\mathfrak{a},M)\) is a finitely generated \(R\)-module for every \(i\geq 0\). Moreover, recall that \[\operatorname{cd}(\mathfrak{a},M)=\sup\{i \geq 0\mid H^{i}_{\mathfrak{a}}(M)\neq 0\},\] and \[\operatorname{q}(\mathfrak{a},M)=\sup\{i \geq 0\mid H^{i}_{\mathfrak{a}}(M) \text{ is not artinian}\}.\] Now suppose that \(M\) and \(N\) are finitely generated. The authors prove that if \(\operatorname{cd}(\mathfrak{a},R)\leq 1\) and \(M\) has finite projective dimension, then \(H^{i}_{\mathfrak{a}}(M,N)\) is \(\mathfrak{a}\)-cofinite for every \(i\geq 0\). Furthermore, they show that if \(\operatorname{q}(\mathfrak{a},R)\leq 1\) and \(M\) has finite projective dimension, then the Bass numbers of \(H^{i}_{\mathfrak{a}}(M,N)\) are all finite for every \(i\geq 0\). Finally, they characterize the greatest integer \(i\) for which \(H^{i}_{\mathfrak{a}}(M,N)\) is not artinian and \(\mathfrak{a}\)-cofinite.
13D45, 14B15, Bass number, cohomological dimension, noetherian ring, 13E05, generalized local cohomology module, Noetherian ring, Local cohomology and commutative rings, Local cohomology and algebraic geometry, Commutative Noetherian rings and modules, cofinite module
13D45, 14B15, Bass number, cohomological dimension, noetherian ring, 13E05, generalized local cohomology module, Noetherian ring, Local cohomology and commutative rings, Local cohomology and algebraic geometry, Commutative Noetherian rings and modules, cofinite module
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