English

A Pascal's Theorem for rational normal curves

Algebraic Geometry 2021-09-17 v2

Abstract

Pascal's Theorem gives a synthetic geometric condition for six points a,,fa,\ldots,f in P2\mathbb{P}^2 to lie on a conic. Namely, that the intersection points abde\overline{ab}\cap\overline{de}, afdc\overline{af}\cap\overline{dc}, efbc\overline{ef}\cap\overline{bc} are aligned. One could ask an analogous question in higher dimension: is there a coordinate-free condition for d+4d+4 points in Pd\mathbb{P}^d to lie on a degree dd rational normal curve? In this paper we find many of these conditions by writing in the Grassmann-Cayley algebra the defining equations of the parameter space of d+4d+4 ordered points in Pd\mathbb{P}^d that lie on a rational normal curve. These equations were introduced and studied in a previous joint work of the authors with Giansiracusa and Moon. We conclude with an application in the case of seven points on a twisted cubic.

Keywords

Cite

@article{arxiv.1903.00460,
  title  = {A Pascal's Theorem for rational normal curves},
  author = {Alessio Caminata and Luca Schaffler},
  journal= {arXiv preprint arXiv:1903.00460},
  year   = {2021}
}

Comments

17 pages, 1 figure. Final version. To appear in Bulletin of the London Mathematical Society

R2 v1 2026-06-23T07:55:45.077Z