English

Hypersurfaces passing through the Galois orbit of a point

Algebraic Geometry 2026-04-10 v2 Number Theory

Abstract

Asgarli, Ghioca, and Reichstein proved that if KK is a field with K>2|K|>2, then for any positive integers dd and nn, and separable field extension L/KL/K with degree m=(n+dd)m=\binom{n+d}{d}, there exists a point PPn(L)P\in \mathbb{P}^n(L) which does not lie on any degree dd hypersurface defined over KK. They asked whether the result holds when K=2|K| = 2. We answer their question in the affirmative by combining various ideas from arithmetic geometry. More generally, we show that for each positive integer rr and separable field extension L/KL/K with degree rr, there exists a point PPn(L)P \in \mathbb{P}^n(L) such that the vector space of degree dd forms over KK that vanish at PP has the expected dimension. We also discuss applications to linear systems of hypersurfaces with special properties.

Keywords

Cite

@article{arxiv.2501.01906,
  title  = {Hypersurfaces passing through the Galois orbit of a point},
  author = {Shamil Asgarli and Jonathan Love and Chi Hoi Yip},
  journal= {arXiv preprint arXiv:2501.01906},
  year   = {2026}
}

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29 pages