Special precovers and preenvelopes of complexes

Abstract

The notion of an $\mathcal{L}$ complex (for a given class of $R$-modules $\mathcal{L}$) was introduced by Gillespie: a complex $C$ is called $\mathcal{L}$ complex if $C$ is exact and ${\mathbb{Z}}_i(C)$ is in $\mathcal{L}$ for all $i\in \mathbb{Z}$. Let $\tilde{\mathcal{L}}$ stand for the class of all $\mathcal{L}$ complexes. In this paper, we give sufficient condition on a class of $R$-modules such that every complex has a special $\tilde{\mathcal{L}}$-precover (resp., $\tilde{\mathcal{L}}$-preenvelope). As applications, we obtain that every complex has a special projective precover and a special injective preenvelope, over a coherent ring every complex has a special FP-injective preenvelope, and over a noetherian ring every complex has a special $\widetilde{\mathcal{G}\mathcal{I}}$-preenvelope, where $\mathcal{G}\mathcal{I}$ denotes the class of Gorenstein injective modules.

12 pages