English

On the direct summand conjecture and its derived variant

Algebraic Geometry 2017-11-15 v2 Commutative Algebra

Abstract

Andr\'e recently gave a beautiful proof of Hochster's direct summand conjecture in commutative algebra using perfectoid spaces; his two main results are a generalization of the almost purity theorem (the perfectoid Abhyankar lemma) and a construction of certain faithfully flat extensions of perfectoid algebras where "discriminants" acquire all pp-power roots. In this paper, we explain a quicker proof of Hochster's conjecture that circumvents the perfectoid Abhyankar lemma; instead, we prove and use a quantitative form of Scholze's Hebbarkeitssatz (the Riemann extension theorem) for perfectoid spaces. The same idea also leads to a proof of a derived variant of the direct summand conjecture put forth by de Jong.

Keywords

Cite

@article{arxiv.1608.08882,
  title  = {On the direct summand conjecture and its derived variant},
  author = {Bhargav Bhatt},
  journal= {arXiv preprint arXiv:1608.08882},
  year   = {2017}
}

Comments

12 pages, comments welcome

R2 v1 2026-06-22T15:36:38.035Z