Uniform boundedness of rational torsion

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Subjects: Arithmetic geometry

Collections: Fields and rational points

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The problem

On a five-position clock numbered 0 through 4, repeatedly adding 2 visits 2, 4, 1, 3 and then returns to 0. This is a small illustration of finite order under addition, not an example of the geometric objects in the conjecture.

Can one bound the total number of points that return to zero under addition across a whole family of geometric objects, when we fix their dimension and the arithmetic size of their coordinate field?

The objects here are abelian varieties, whose points can be added. A finite-order point returns to zero after being added to itself a positive number of times. The coordinates lie in a number field, a finite extension of the rational numbers; its degree is its dimension over the rationals. The same bound must work for every variety and every field of those fixed sizes.[1]

Scope

For every g≥2 and D≥1, seek B(g,D) with |A(K)tors|≤B(g,D) for every g-dimensional abelian variety over every number field K of degree D.

What remains open

For one-dimensional abelian varieties, called elliptic curves, a common bound depending on the coordinate field’s degree is known. The August preprint’s higher-dimensional number-field result assumes an unproved arithmetic conjecture and an extra condition on how the variety behaves at primes. These restrictions leave the unconditional target open: one bound for all varieties and all number fields of each fixed dimension and degree.[1]

Why it matters

The finite-order points form the finite, periodic part of the rational-point group, alongside points that never return to zero by repeated addition. A uniform bound would constrain that periodic part while both the equations and the coordinate field change. The distinction between controlling one object and a whole family is central to arithmetic geometry.[1]

Definitions

3 terms
torsion point

A point PP for which mP=0mP=0 for some positive integer mm, using the variety’s group law. The target counts all field-rational torsion points, including zero, rather than fixing one order.[1]

abelian variety

A smooth projective algebraic variety equipped with a commutative algebraic group law. Points defined over the chosen field can be added; elliptic curves are the dimension-one case.[1]

number field

A field that is a finite extension of the rational numbers. Its degree is its vector-space dimension over the rationals; the bound must be uniform over all fields of that degree.[1]

Sources

  1. Uniformity in rational torsion and small points on abelian varieties Ziyang Gao and Kaiyuan Gu · 2026-08-23
    Notes on Uniformity in rational torsion and small points on abelian varieties

    Conjecture1.1 and conditional Theorem1.9 identify the remaining number-field scope.

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