4 papers
Weakly Sigma-cotorsion rings
Manuel Cortés-Izurdiaga, Sergio Estrada, José Manuel Fresneda
We study the class of rings for which every direct sum of injective -modules is cotorsion. We call them weakly -cotorsion rings. The defining property might be seen as t…
Acyclic complexes and regular rings
Lars Winther Christensen, Sergio Estrada, Peder Thompson
A 2009 paper by Iacob and Iyengar characterizes noetherian regular rings in terms of properties of complexes of projective modules, flat modules, and injective modules. We show tha…
Gorenstein categories relative to G-admissible triples
Sergio Estrada, Octavio Mendoza, Marco A. Pérez
We present the notion of Gorenstein categories relative to G-admissible triples. This is a relativization of the concept of Gorenstein category (an abelian category with enough pro…
Powers of ghost ideals
S. Estrada, X. H. Fu, I. Herzog +1
A theory of ordinal powers of the ideal of -ghost morphisms is developed by introducing for every ordinal , the -th inductive powe…