Cohomology theories for complexes

Abstract

We introduce and study a complete cohomology theory for complexes, which provides an extended version of Tate-Vogel cohomology in the setting of (arbitrary) complexes over associative rings. Moreover, for complexes of finite Gorenstein projective dimension a notion of relative Ext is introduced. On the basis of these cohomology groups, some homological invariants of modules over commutative noetherian local rings, such as Martsinkovsky's ξ-invariants and relative and Tate versions of Betti numbers, are extended to the framework of complexes with finite homology. The relation of these invariants with their prototypes is explored. © 2006 Elsevier Ltd. All rights reserved.