English

Two improvements in Brauer's theorem on forms

Number Theory 2024-01-05 v1 Algebraic Geometry

Abstract

Let kk be a Brauer field, that is, a field over which every diagonal form in sufficiently many variables has a nonzero solution; for instance, kk could be an imaginary quadratic number field. Brauer proved that if f1,,frf_1, \ldots, f_r are homogeneous polynomials on a kk-vector space VV of degrees d1,,drd_1, \ldots, d_r, then the variety ZZ defined by the fif_i's has a non-trivial kk-point, provided that dimV\dim{V} is sufficiently large compared to the did_i's and kk. We offer two improvements to this theorem, assuming kk is infinite. First, we show that the Zariski closure of the set Z(k)Z(k) of kk-points has codimension <C<C, where CC is a constant depending only on the did_i's and kk. And second, we show that if the strength of the fif_i's is sufficiently large in terms of the did_i's and kk, then Z(k)Z(k) is actually Zariski dense in ZZ. The proofs rely on recent work of Ananyan and Hochster on high strength polynomials.

Keywords

Cite

@article{arxiv.2401.02067,
  title  = {Two improvements in Brauer's theorem on forms},
  author = {Arthur Bik and Jan Draisma and Andrew Snowden},
  journal= {arXiv preprint arXiv:2401.02067},
  year   = {2024}
}

Comments

22 pages

R2 v1 2026-06-28T14:08:22.313Z