Relative Gorenstein flat modules and Foxby classes and their model structures

TL;DR

This paper develops new relative Gorenstein flat and cotorsion modules, constructs hereditary abelian model structures on module categories, and explores their properties using Bass and Auslander classes, advancing homotopy theory in algebra.

Contribution

It introduces and studies new concepts of relative Gorenstein cotorsion modules and constructs unique hereditary abelian model structures on module categories.

Findings

Existence of a unique hereditary abelian model structure with specific cofibrations and fibrations.

Characterization of G_C-flat modules and Bass classes within weak AB-contexts.

Dual results involving G_C-cotorsion modules and Auslander classes.

Abstract

A model structure on a category is a formal way of introducing a homotopy theory on that category, and if the model structure is abelian and hereditary, its homotopy category is known to be triangulated. So a good way to both build and model a triangulated category is to build a hereditary abelian model structure. Given a ring $R$ and a (non necessarily semidualizing) left $R$-module $C$, we introduce and study new concepts of relative Gorenstein cotorsion and cotorsion modules: $\rm G_C$-cotorsion and (strongly) $\mathcal{C}_C$-cotorsion. As an application, we prove that there is a unique hereditary abelian model structure on the category of left $R$-modules, in which the cofibrations are the monomorphisms with $\rm G_C$-flat cokernel and the fibrations are the epimorphisms with $\mathcal{C}_C$-cotorsion kernel belonging to the Bass class $\mathcal{B}_C(R)$. In the second part, when $C$ is a semidualizing $(R,S)$-bimodule, we investigate the existence of abelian model structures on the category of left (resp., right) $R$-modules where the cofibrations are the epimorphisms (resp., monomorphisms) with kernel (resp., cokernel) belonging to the Bass (resp., Auslander) class $\mathcal{B}_C(R)$ (resp., $\mathcal{A}_C(R)$). We also study the class of $\rm G_C$-flat modules and the Bass class from the Auslander-Buchweitz approximation theory point of view. We show that they are part of weak AB-contexts. As the concept of weak AB-context can be dualized, we also give dual results that involve the class of $\rm G_C$-cotorsion modules and the Auslander class.