English

Extended plus closure in complete local rings

Commutative Algebra 2018-10-24 v3

Abstract

The (full) extended plus closure was developed as a replacement for tight closure in mixed characteristic rings. Here it is shown by adapting Andr\'{e}'s perfectoid algebra techniques that, for complete local rings that have F-finite residue fields, this closure has the colon-capturing property. In fact, more generally, if RR is a (possibly ramified) complete regular local ring of mixed characteristic that have F-finite residue fields, II and JJ are ideals of RR, and the local domain SS is a finite RR-module, then (IS:J)(I:J)Sepf(IS:J)\subseteq (I:J)S^{epf}. A consequence is that all ideals in regular local rings are closed, a fact which implies the validity of the direct summand conjecture and the Brian\c{c}on-Skoda theorem in mixed characteristic.

Keywords

Cite

@article{arxiv.1708.05761,
  title  = {Extended plus closure in complete local rings},
  author = {Raymond Heitmann and Linquan Ma},
  journal= {arXiv preprint arXiv:1708.05761},
  year   = {2018}
}

Comments

Some new applications added, and the hypothesis for the residue field to be F-finite was added to several results

R2 v1 2026-06-22T21:18:21.144Z