English

Support and adic finiteness for complexes

Commutative Algebra 2015-06-08 v3

Abstract

Let XX be a chain complex over a commutative noetherian ring RR, that is, an object in the derived category D(R)\mathcal{D}(R). We investigate the small support and co-support of XX, introduced by Foxby and Benson, Iyengar, and Krause. We show that the derived functors MRLM \otimes_R^{\mathbf{L}} - and RHomR(M,)\mathbf{R}\operatorname{Hom}_R(M,-) can detect isomorphisms in D(R)\mathcal{D}(R) between complexes with restrictions on their supports or co-supports. In particular, the derived local (co)homology functors RΓa()\mathbf{R}\Gamma_{\mathfrak{a}}(-) and LΛa()\mathbf{L}\Lambda_{\mathfrak{a}}(-) with respect to an ideal aR\mathfrak{a}\subsetneq R have the same ability. Furthermore, we give reprove some results of Benson, Iyengar, and Krause in our setting, with more direct proofs. Also, we include some computations of co-supports, since this construction is still quite mysterious. Lastly, we investigate "a\mathfrak{a}-adically finite" RR-complexes, that is, the XD(R)X\in\mathcal{D}(R) that are a\mathfrak{a}-cofinite \textit{\`a la} Hartshorne. For instance, we characterize these complexes in terms of a finiteness condition on LΛa(X)\mathbf{L}\Lambda_{\mathfrak{a}}(X).

Keywords

Cite

@article{arxiv.1401.6925,
  title  = {Support and adic finiteness for complexes},
  author = {Sean Sather-Wagstaff and Richard Wicklein},
  journal= {arXiv preprint arXiv:1401.6925},
  year   = {2015}
}

Comments

26 pages, v.2 is significantly reorganized; v.3 addresses referee's comments. To appear in Comm. Algebra

R2 v1 2026-06-22T02:55:35.734Z