English

Vanishing of Tors of absolute integral closures in equicharacteristic zero

Commutative Algebra 2022-12-20 v1

Abstract

We show that a ring RR is regular if ToriR(R+,k)=0Tor_{i}^{R}(R^{+},k) = 0 for some i1i\geq 1 assuming further that RR is a N\mathbb{N}-graded ring of dimension 22 finitely generated over an equi-characteristic zero field kk. This answers a question of Bhatt, Iyengar, and Ma. We use almost mathematics over R+R^{+} to deduce properties of the noetherian ring RR and rational surface singularities. Moreover we show that R+R^{+} in equi-characteristic zero is mm-adically ideal(wise) separated, a condition which appears in the proof of local criterion for flatness. In dimension 22 it is Ohm-Rush and intersection flat. As an application we show that the hypothesis can be astonishingly vacuous for idim(R)i \ll dim(R). We show that a positive answer to an old question of Aberbach and Hochster also answers this question. We use our techniques to make some remarks on a question of Andr\'e and Fiorot regarding `fpqc analgoues' of splinters.

Keywords

Cite

@article{arxiv.2212.09025,
  title  = {Vanishing of Tors of absolute integral closures in equicharacteristic zero},
  author = {Shravan Patankar},
  journal= {arXiv preprint arXiv:2212.09025},
  year   = {2022}
}

Comments

19 pages. Comments, questions, and suggestions welcome