English

Strictly nef divisors on singular threefolds

Algebraic Geometry 2021-06-18 v2

Abstract

Let XX be a normal projective threefold with mild singularities, and LXL_X a strictly nef Q\mathbb{Q}-divisor on XX. First, we show the ampleness of KX+tLXK_X+tL_X with sufficiently large tt if either the Kodaira dimension κ(X)0\kappa(X)\neq 0 or the augmented irregularity q(X)0q^{\circ}(X)\neq 0. Second, we show that, if (X,Δ)(X,\Delta) is a projective klt threefold pair with the anti-log canonical divisor (KX+Δ)-(K_X+\Delta) being strictly nef, then XX is rationally connected.

Keywords

Cite

@article{arxiv.2105.07681,
  title  = {Strictly nef divisors on singular threefolds},
  author = {Guolei Zhong},
  journal= {arXiv preprint arXiv:2105.07681},
  year   = {2021}
}

Comments

28 pages; Theorem 1.7 has been strengthened and Section 6 has been greatly shortened and improved; comments are welcome!

R2 v1 2026-06-24T02:10:15.655Z