Cohen-Macaulay modules, (co)torsion pairs and virtually Gorenstein algebras

We use torsion pairs in stable categories and cotorsion pairs in modules categories to study, in General infinitely generated, Cohen-Macaulay modules and (a generalization of) modules of finite projective or injective dimension over an Artin algebra. We concentrate our investigation to the study of virtually Gorenstein algebras which provide a common generalization of Gorenstein algebras and aluebras of finite representation or Cohen-Macaulay type. This class of algebras on the one hand has rich homological structure and satisfies several representation/torsion theoretic finiteness conditions, and on the other hand it is closed under various operations, for instance derived equivalences and stable equivalences of Morita type. In addition virtual Gorensteinness provides a useful tool for the study of the Gorenstein Symmetry Conjecture and modified versions of the Telescope Conjecture for module or stable categories. (c) 2005 Elsevier Inc. All rights reserved.