English

Remarks on polynomial count varieties

Number Theory 2026-03-10 v1 Algebraic Geometry

Abstract

In this short note we prove a couple of facts about polynomial count varieties, answering natural questions that they raise. A polynomial count XX variety is essentially one for which its number of points over finite fields is given by a polynomial in the field size. Well-known examples include affine or projective space (or more generally the Grassmanian) and other standard varieties. The two questions we address are the following. 1) If XX is smooth, polynomial count with #X(q)=qn\#X(q)=q^n for some nn, is XX isomorphic to nn-dimensional affine space? 2) If XX is a polynomial count, is it true that its Hodge numbers in a given graded piece of fixed weight satisfy~hp,q=0h^{p,q}=0 unless p=qp=q? We show that in both cases the answer is no.

Keywords

Cite

@article{arxiv.2603.07062,
  title  = {Remarks on polynomial count varieties},
  author = {Nicholas M. Katz and Fernando Rodriguez Villegas},
  journal= {arXiv preprint arXiv:2603.07062},
  year   = {2026}
}
R2 v1 2026-07-01T11:08:17.370Z