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

Fuente: arXiv
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Autori principali: Desjardins, Julie, Winter, Rosa
Natura: Preprint
Pubblicazione: 2022
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author Desjardins, Julie
Winter, Rosa
author_facet Desjardins, Julie
Winter, Rosa
contents The blow-up of the anticanonical base point on a del Pezzo surface $S$ of degree 1 gives rise to a rational elliptic surface $\mathscr{E}$ with only irreducible fibers. The sections of minimal height of $\mathscr{E}$ are in correspondence with the $240$ exceptional curves on $S$. A natural question arises when studying the configuration of these curves: if a point on $S$ is contained in 'many' exceptional curves, it is torsion on its fiber on $\mathscr{E}$? In 2005, Kuwata proved for the analogous question on del Pezzo surfaces of degree $2$, where there are 56 exceptional curves, that if 'many' equals $4$ 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 $9$ or more. Moreover, we give counterexamples where a \textsl{non}-torsion point lies in the intersection of $7$ exceptional curves. We give partial results for the still open case of 8 intersecting exceptional curves.
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id arxiv_https___arxiv_org_abs_2210_11659
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Torsion points and concurrent exceptional curves on del Pezzo surfaces of degree one
Desjardins, Julie
Winter, Rosa
Algebraic Geometry
Number Theory
The blow-up of the anticanonical base point on a del Pezzo surface $S$ of degree 1 gives rise to a rational elliptic surface $\mathscr{E}$ with only irreducible fibers. The sections of minimal height of $\mathscr{E}$ are in correspondence with the $240$ exceptional curves on $S$. A natural question arises when studying the configuration of these curves: if a point on $S$ is contained in 'many' exceptional curves, it is torsion on its fiber on $\mathscr{E}$? In 2005, Kuwata proved for the analogous question on del Pezzo surfaces of degree $2$, where there are 56 exceptional curves, that if 'many' equals $4$ 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 $9$ or more. Moreover, we give counterexamples where a \textsl{non}-torsion point lies in the intersection of $7$ exceptional curves. We give partial results for the still open case of 8 intersecting exceptional curves.
title Torsion points and concurrent exceptional curves on del Pezzo surfaces of degree one
topic Algebraic Geometry
Number Theory
url https://arxiv.org/abs/2210.11659