English

A Mehta-Ramanathan theorem for linear systems with basepoints

Algebraic Geometry 2020-11-05 v2

Abstract

Let (X,H)(X, H) be a normal complex projective polarized variety and E\mathscr E an HH-semistable sheaf on XX. We prove that the restriction EC\mathscr E\big|_C to a sufficiently positive general complete intersection curve CXC \subset X passing through a prescribed finite set of points SXS \subset X remains semistable, provided that at each pSp \in S, the variety XX is smooth and the factors of a Jordan-H\"older filtration of E\mathscr E are locally free. As an application, we obtain a generalization of Miyaoka's generic semipositivity theorem.

Keywords

Cite

@article{arxiv.1501.04210,
  title  = {A Mehta-Ramanathan theorem for linear systems with basepoints},
  author = {Patrick Graf},
  journal= {arXiv preprint arXiv:1501.04210},
  year   = {2020}
}

Comments

Mostly minor changes. Improved Example 1.9. To appear in Mathematische Nachrichten

R2 v1 2026-06-22T08:04:33.861Z