English

Singular rationally connected threefolds with non-zero pluri-forms

Algebraic Geometry 2014-01-10 v1

Abstract

This paper is concerned with singular projective rationally connected threefolds XX which carry non-zero pluri-forms, \textit{i.e.} H0(X,(ΩX1)[m]){0}H^0(X,(\Omega_X^1)^{[\otimes m]}) \neq \{0\} for some m>0m > 0, where (ΩX1)[m](\Omega_X^1)^{[\otimes m]} is the reflexive hull of (ΩX1)m(\Omega_X^1)^{\otimes m}. If XX has Q\mathbb{Q}-factorial terminal singularities, then we show that there is a fibration pp from XX to P1\mathbb{P}^1. Moreover, there is a natural isomorphism from H0(X,(ΩX1)[m])H^0(X, (\Omega_X^1)^{[\otimes m]}) to H0(P1,OP1(2m+zP1[(m(p,z)1)mm(p,z)]))H^0(\mathbb{P}^1, \mathscr{O}_{\mathbb{P}^1}(-2m+\sum_{z\in \mathbb{P}^1} [\frac{(m(p,z)-1)m}{m(p,z)}])) for all m>0m>0, where m(p,z)m(p,z) is the smallest positive coefficient in the divisor pzp^*z.

Keywords

Cite

@article{arxiv.1401.2014,
  title  = {Singular rationally connected threefolds with non-zero pluri-forms},
  author = {Wenhao Ou},
  journal= {arXiv preprint arXiv:1401.2014},
  year   = {2014}
}

Comments

15 pages

R2 v1 2026-06-22T02:42:08.409Z