English

Torsion points and concurrent exceptional curves on del Pezzo surfaces of degree one

Algebraic Geometry 2025-04-30 v4 Number Theory

Abstract

The blow-up of the anticanonical base point on a del Pezzo surface SS of degree 1 gives rise to a rational elliptic surface E\mathscr{E} with only irreducible fibers. The sections of minimal height of E\mathscr{E} are in correspondence with the 240240 exceptional curves on SS. A natural question arises when studying the configuration of these curves: if a point on SS is contained in 'many' exceptional curves, it is torsion on its fiber on E\mathscr{E}? In 2005, Kuwata proved for the analogous question on del Pezzo surfaces of degree 22, where there are 56 exceptional curves, that if 'many' equals 44 or more, the answer is yes. In this paper, we prove that for del Pezzo surfaces of degree 1, the answer is yes if 'many' equals 99 or more. Moreover, we give counterexamples where a \textsl{non}-torsion point lies in the intersection of 77 exceptional curves. We give partial results for the still open case of 8 intersecting exceptional curves.

Keywords

Cite

@article{arxiv.2210.11659,
  title  = {Torsion points and concurrent exceptional curves on del Pezzo surfaces of degree one},
  author = {Julie Desjardins and Rosa Winter},
  journal= {arXiv preprint arXiv:2210.11659},
  year   = {2025}
}

Comments

14 pages, published in CBM