Torsion phenomena for zero-cycles on a product of curves over a number field

TL;DR

This paper investigates torsion phenomena for zero-cycles on products of curves over number fields, proving a conjecture for such products based on subproducts and providing new examples of elliptic curves with finite zero-cycle images.

Contribution

It proves the Bloch-Beilinson conjecture for products of curves assuming it for two-curve subproducts and constructs new examples of elliptic curves with finite zero-cycle images.

Findings

Conjecture holds for products if true for all two-curve subproducts.

Constructed many non-isogenous elliptic curves with finite zero-cycle images.

Produced infinitely many products with finite zero-cycle images.

Abstract

For a smooth projective variety $X$ over a number field $k$ a conjecture of Bloch and Beilinson predicts that the kernel of the Albanese map of $X$ is a torsion group. In this article we consider a product $X=C_1\times\cdots\times C_d$ of smooth projective curves and show that if the conjecture is true for any subproduct of two curves, then it is true for $X$. Additionally, we produce many new examples of non-isogenous elliptic curves $E_1, E_2$ with positive rank over $\mathbb{Q}$ for which the image of the natural map $E_1(\mathbb{Q})\otimes E_2(\mathbb{Q})\xrightarrow{\varepsilon} \text{CH}_0(E_1\times E_2)$ is finite, including the first known examples of rank greater than $1$. Combining the two results, we obtain infinitely many nontrivial products $X=C_1\times\cdots\times C_d$ for which the analogous map $\varepsilon$ has finite image.