English

On complete integral closedness of the $p$-adic completion of absolute integral closure

Commutative Algebra 2026-02-04 v2

Abstract

Fix a prime pp and let (R,m)(R,\mathfrak{m}) be a Noetherian complete local domain of mixed characteristic (0,p)(0,p) with fraction field KK. Let R+R^+ denote the absolute integral closure of RR, which is the integral closure of RR in an algebraic closure K\overline{K} of KK. The first author has shown that R+^\widehat{R^+}, the pp-adic completion of R+R^+, is an integral domain. In this paper, we prove that R+^\widehat{R^+} is completely integrally closed in R+^R+K\widehat{R^+}\otimes_{R^+}\overline{K}, but R+^\widehat{R^+} is not completely integrally closed in its own fraction field when dim(R)2\dim(R)\geq 2.

Keywords

Cite

@article{arxiv.2506.19148,
  title  = {On complete integral closedness of the $p$-adic completion of absolute integral closure},
  author = {Raymond Heitmann and Linquan Ma},
  journal= {arXiv preprint arXiv:2506.19148},
  year   = {2026}
}

Comments

15 pages, minor updates, final version