We define the notion of an additive model category and prove that any stable, additive, combinatorial model category $\cal M$ has a model enrichment over $Sp^\Sigma(sAb)$ (symmetric spectra based on simplicial abelian groups). So to any object $X$ in $\cal M$ one can attach an endomorphism ring object, denoted $hEnd_ad(X)$, in the category $Sp^\Sigma(sAb)$. We establish some useful properties of these endomorphism rings.
We also develop a new notion in enriched category theory which we call `adjoint modules'. This is used to compare enrichments over one symmetric monoidal model category with enrichments over a Quillen equivalent one. In particular, it is used here to compare enrichments over $\Sp^\Sigma(s\Ab)$ and chain complexes.
Keywords: model categories, symmetric spectra, endomorphism ring
2000 MSC: 18D20, 55U35, 55P42, 18E05
Theory and Applications of Categories,
Vol. 18, 2007,
No. 15, pp 400-439.