English

Intersection of complete cotorsion pairs

K-Theory and Homology 2026-02-20 v2

Abstract

Given two (hereditary) complete cotorsion pairs (X1,Y1)(\mathcal{X}_1,\mathcal{Y}_1) and (X2,Y2)(\mathcal{X}_2,\mathcal{Y}_2) in an exact category with X1Y2\mathcal{X}_1\subseteq \mathcal{Y}_2, we prove that (SmdX1,X2,Y1Y2)\left({\rm Smd}\langle \mathcal{X}_1,\mathcal{X}_2 \rangle,\mathcal{Y}_1\cap \mathcal{Y}_2\right) is also a (hereditary) complete cotorsion pair, where SmdX1,X2{\rm Smd}\langle \mathcal{X}_1,\mathcal{X}_2 \rangle is the class of direct summands of extension of X1\mathcal{X}_1 and X2\mathcal{X}_2. As an application, we construct complete cotorsion pairs, such as (GIn,GIn)(^\perp\mathcal{GI}^{\leqslant n},\mathcal{GI}^{\leqslant n}), where GIn\mathcal{GI}^{\leqslant n} is the class of modules of Gorenstein injective dimension at most nn. And we also characterize the left orthogonal class of exact complexes of injective modules and the classes of modules with finite Gorenstein projective, Gorenstein flat, and PGF dimensions.

Cite

@article{arxiv.2408.01922,
  title  = {Intersection of complete cotorsion pairs},
  author = {Qikai Wang and Haiyan Zhu},
  journal= {arXiv preprint arXiv:2408.01922},
  year   = {2026}
}
R2 v1 2026-06-28T18:03:19.296Z