When are KE-closed subcategories torsion-free classes?

Let R be a commutative noetherian ring and denote by \mathsf{mod} R the category of finitely generated R-modules. In this paper, we study KE-closed subcategories of \mathsf{mod} R, that is, additive subcategories closed under kernels and extensions. We first give a characterization of KE-closed subcategories: a KE-closed subcategory is a... Show more