English

Degrees of closed points on hypersurfaces

Number Theory 2023-07-24 v2

Abstract

Let kk be any field. Let XPkNX \subset \mathbb{P}_k^N be a degree d2d \geq 2 hypersurface. Under some conditions, we prove that if X(K)X(K) \neq \emptyset for some extension K/kK/k with n:=[K:k]2n:=[K:k] \geq 2 and gcd(n,d)=1\gcd(n,d)=1, then X(L)X(L) \neq \emptyset for some extension L/kL/k with gcd([L:k],d)=1\gcd([L:k], d)=1, n[L:k]n \nmid [L:k], and [L:k]ndnd[L:k] \leq nd-n-d. Moreover, if a KK-solution is known explicitly, then we can compute L/kL/k explicitly as well. As an application, we improve upon a result by Coray on smooth cubic surfaces XPk3X \subset \mathbb{P}^3_k by showing that if X(K)X(K) \neq \emptyset for some extension K/kK/k with gcd([K:k],3)=1\gcd([K:k], 3)=1, then X(L)X(L) \neq \emptyset for some L/kL/k with [L:k]{1,10}[L:k] \in \{1, 10\}.

Keywords

Cite

@article{arxiv.2304.04562,
  title  = {Degrees of closed points on hypersurfaces},
  author = {Francesca Balestrieri},
  journal= {arXiv preprint arXiv:2304.04562},
  year   = {2023}
}

Comments

The structure of the paper has been changed and the main theorem is now the one for the more general case; suggestions and comments from the referees have been incorporated

R2 v1 2026-06-28T09:57:17.787Z