English

Local cohomology properties of direct summands

Commutative Algebra 2012-07-10 v2

Abstract

In this article, we prove that if RSR\to S is a homomorphism of Noetherian rings that splits, then for every i0i\geq 0 and ideal IRI\subset R, \AssRHIi(R)\Ass_R H^i_I(R) is finite when \AssSHISi(S)\Ass_S H^i_{IS}(S) is finite. In addition, if SS is a Cohen-Macaulay ring that is finitely generated as an RR-module, such that all the Bass numbers of HISi(S)H^i_{IS}(S), as an SS-module, are finite, then all the Bass numbers of HIi(R)H^i_{I}(R), as an RR-module, are finite. Moreover, we show these results for a larger class a functors introduced by Lyubeznik. As a consequence, we exhibit a Gorenstein FF-regular UFD of positive characteristic that is not a direct summand, not even a pure subring, of any regular ring.

Keywords

Cite

@article{arxiv.1108.4455,
  title  = {Local cohomology properties of direct summands},
  author = {Luis Nunez-Betancourt},
  journal= {arXiv preprint arXiv:1108.4455},
  year   = {2012}
}

Comments

8 pages. References updated. Minor changes