English

Bertini's theorem for $F$-rational $F$-pure singularities

Algebraic Geometry 2025-09-30 v2 Commutative Algebra

Abstract

Let kk be an algebraically closed field of characteristic p>0p>0, and let XPknX\subseteq\mathbb{P}^n_k be a quasi-projective variety that is FF-rational and FF-pure. We prove that if HPknH \subseteq \mathbb{P}^n_k is a general hyperplane, then XHX \cap H is also FF-rational and FF-pure. Of related but independent interest, we present a relationship between the characteristic and index of a Q\mathbb{Q}-Gorenstein variety with isolated non-FF-regular locus which is FF-pure but not FF-regular.

Keywords

Cite

@article{arxiv.2509.04433,
  title  = {Bertini's theorem for $F$-rational $F$-pure singularities},
  author = {Alessandro De Stefani and Thomas Polstra and Austyn Simpson},
  journal= {arXiv preprint arXiv:2509.04433},
  year   = {2025}
}

Comments

v1: 16 pages, comments welcome v2: major revision. Added Section 3; Lemma 3.1 of v1 has been replaced with Theorem 3.1 and Lemma 4.1; both main theorems are unaffected. 17 pages, comments welcome

R2 v1 2026-07-01T05:21:40.967Z