Counting Rational Points on Danielewski and Double Danielewski Surfaces over Finite Fields

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Hauptverfasser: Gupta, Sakshi, Kuckian, Anit, Sengupta, Indranath
Format: Preprint
Veröffentlicht: 2026
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author Gupta, Sakshi
Kuckian, Anit
Sengupta, Indranath
author_facet Gupta, Sakshi
Kuckian, Anit
Sengupta, Indranath
contents Let $\Fq$ be the finite field with $q$ elements. We study the number of $\Fq$-rational points on Danielewski and double Danielewski surfaces. For Danielewski surfaces, the point count is reduced to the number of roots of $P(Z)$ over $\Fq.$ For double Danielewski surfaces, one has to count the number of tuples $(\be,\g)\in\Fq^2$, such that $P(0,\g)=0$, $Q(0,\be,\g)=0$ hold simultaneously. We compute these numbers using gcd methods, resultants, character sums, Gauss sums, and the König--Rados theorem. We obtain explicit formulas in several structured cases, derive general bounds, and give a Macaulay2 algorithm for verification and show an intresting connection between the number of $\Fq$-rational points of these surfaces and polygonal numbers.
format Preprint
id arxiv_https___arxiv_org_abs_2605_24821
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Counting Rational Points on Danielewski and Double Danielewski Surfaces over Finite Fields
Gupta, Sakshi
Kuckian, Anit
Sengupta, Indranath
Number Theory
Commutative Algebra
11T06, 11T99
Let $\Fq$ be the finite field with $q$ elements. We study the number of $\Fq$-rational points on Danielewski and double Danielewski surfaces. For Danielewski surfaces, the point count is reduced to the number of roots of $P(Z)$ over $\Fq.$ For double Danielewski surfaces, one has to count the number of tuples $(\be,\g)\in\Fq^2$, such that $P(0,\g)=0$, $Q(0,\be,\g)=0$ hold simultaneously. We compute these numbers using gcd methods, resultants, character sums, Gauss sums, and the König--Rados theorem. We obtain explicit formulas in several structured cases, derive general bounds, and give a Macaulay2 algorithm for verification and show an intresting connection between the number of $\Fq$-rational points of these surfaces and polygonal numbers.
title Counting Rational Points on Danielewski and Double Danielewski Surfaces over Finite Fields
topic Number Theory
Commutative Algebra
11T06, 11T99
url https://arxiv.org/abs/2605.24821