English

Curves on irrational ruled surfaces whose complements are of non-general type

Algebraic Geometry 2026-06-27 v1

Abstract

Let BB be a curve on an irrational ruled surface XX. We prove that the logarithmic Kodaira dimension of XBX-B equals the Iitaka dimension of KX+BK_X+B and give a rough configuration of BB when the logarithmic Kodaira dimension of XBX - B is less than two. Next, we study the logarithmic multicanonical system of XBX-B when the logarithmic Kodaira dimension of XBX - B equals one and prove that its logarithmic mm-canonical system gives either a P1\mathbb{P}^1-fibration or an elliptic fibration if m12m \geq 12.

Keywords

Cite

@article{arxiv.2606.28803,
  title  = {Curves on irrational ruled surfaces whose complements are of non-general type},
  author = {Hideo Kojima},
  journal= {arXiv preprint arXiv:2606.28803},
  year   = {2026}
}

Comments

21 pages, one figure