<p>Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathfrak {\textrm{a}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mtext mathvariant="fraktur">a</mtext> </math></EquationSource> </InlineEquation> be an ideal of a commutative Noetherian ring <i>R</i>. In this paper, we provide some equivalent conditions for the category of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathfrak {\textrm{a}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mtext mathvariant="fraktur">a</mtext> </math></EquationSource> </InlineEquation>-cofinite modules being an Abelian subcategory of the category of all <i>R</i>-modules. This result provides a solution for the second problem of R. Hartshorne in [<i>Affine duality and cofiniteness</i>, Invent. Math. <b>9</b>(1970), 145-164].</p>
When the category of cofinite modules with respect to an ideal is Abelian?
Let \(\mathfrak {\textrm{a}}\) be an ideal of a commutative Noetherian ring R. In this paper, we provide some equivalent conditions for the category of \(\mathfrak {\textrm{a}}\)-cofinite modules being an Abelian subcategory of the category of all R-modules. This result provides a solution for the second problem of R. Hartshorne in [Affine duality and cofiniteness, Invent. Math. 9(1970), 145-164].