The dimension growth conjecture, polynomial in the degree and without logarithmic factors

Castryck, Wouter; Cluckers, Raf; Dittmann, Philip; Nguyen, Kien Huu

doi:10.2140/ant.2020.14.2261

Download this article
	For screen
	For printing

Recent Issues

The Journal

About the journal

Ethics and policies

Peer-review process

Submission guidelines

ISSN 1944-7833 (online)

ISSN 1937-0652 (print)

Author index

To appear

Other MSP journals

The dimension growth conjecture, polynomial in the degree and without logarithmic factors

Wouter Castryck, Raf Cluckers, Philip Dittmann and Kien Huu Nguyen

Vol. 14 (2020), No. 8, 2261–2294

DOI: 10.2140/ant.2020.14.2261

Abstract

We study Heath-Brown’s and Serre’s dimension growth conjecture (proved by Salberger) when the degree $d$ grows. Recall that Salberger’s dimension growth results give bounds of the form $O_{X, 𝜀} (B^{dim X + 𝜀})$ for the number of rational points of height at most $B$ on any integral subvariety $X$ of $ℙ_{ℚ}^{n}$ of degree $d \geq 2$ , where one can write $O_{d, n, 𝜀}$ instead of $O_{X, 𝜀}$ as soon as $d \geq 4$ . We give the following simplified and strengthened forms of these results: we remove the factor $B^{𝜀}$ as soon as $d \geq 5$ , we obtain polynomial dependence on $d$ of the implied constant, and we give a simplified, self-contained approach for $d \geq 16$ . Along the way, we improve the well-known bounds due to Bombieri and Pila on the number of integral points of bounded height on affine curves and those by Walsh on the number of rational points of bounded height on projective curves. This leads to a slight sharpening of a recent estimate due to Bhargava, Shankar, Taniguchi, Thorne, Tsimerman and Zhao on the size of the $2$ -torsion subgroup of the class group of a degree $d$ number field. Our treatment builds on recent work by Salberger, who brings in many primes in Heath-Brown’s variant of the determinant method, and on recent work by Walsh and by Ellenberg and Venkatesh who bring in the size of the defining polynomial. We also obtain lower bounds showing that one cannot do better than polynomial dependence on $d$ .

Keywords

dimension growth conjecture, rational points of bounded height

Mathematical Subject Classification 2010

Primary: 11D45

Secondary: 11G35, 14G05

Milestones

Received: 4 February 2020

Accepted: 23 April 2020

Published: 18 September 2020

Authors

Wouter Castryck
KU Leuven imec-COSIC Leuven, Belgium	Ghent University Department of Mathematics: Algebra and Geometry Ghent, Belgium

Raf Cluckers
University of Lille CNRS, UMR 8524 – Laboratoire Painlevé Lille France	KU Leuven Department of Mathematics Leuven, Belgium

Philip Dittmann
Technische Universität Dresden Institut für Algebra Dresden, Germany

Kien Huu Nguyen
KU Leuven Department of Mathematics Leuven Belgium	Thang Long Institute of Mathematics and Applied Sciences Hanoi Vietnam

Vol. 14, No. 8, 2020