Verdier quotients of homotopy categories of rings and Gorenstein-projective precovers

Abstract

Let $R$ be a ring, $\textrm{Proj}$ be the class of all projective right $R$-modules, $\mathcal K$ be the full subcategory of the homotopy category $\mathbf K(\textrm{Proj})$ whose class of objects consists of all totally acyclic complexes, and $\textrm{Mor}_{\mathcal K}$ be the class of all morphisms in $\mathbf K(\textrm{Proj})$ whose cones belong to $\mathcal K$. We prove that if $\mathbf K(\textrm{Proj})$ has enough $\textrm{Mor}_{\mathcal K}$-injective objects, then the Verdier quotient $\mathbf K(\textrm{Proj})/\mathcal K$ has small Hom-sets, and this last condition implies the existence of Gorenstein-projective precovers in $\textrm{Mod-}R$ and of totally acyclic precovers in $\mathbf C(\textrm{Mod-}R)$.