Volume 297, Issue 5 pp. 1831-1837
ORIGINAL ARTICLE

Degrees of closed points on hypersurfaces

Francesca Balestrieri

Corresponding Author

Francesca Balestrieri

Department of Computer Science, Math and Environmental Science, The American University of Paris, Paris, France

Correspondence

Francesca Balestrieri, Department of Computer Science, Math and Environmental Science, The American University of Paris, 5 Boulevard de La Tour-Maubourg, 75007 Paris, France.

Email: [email protected]

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First published: 28 December 2023

Abstract

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

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