Cycles on abelian 2n-folds of Weil type from secant sheaves on abelian n-folds

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1. Verfasser: Markman, Eyal
Format: Preprint
Veröffentlicht: 2025
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author Markman, Eyal
author_facet Markman, Eyal
contents A. Weil identified a 2-dimensional space of rational classes of Hodge type (n,n) in the middle cohomology of every 2n-dimensional abelian variety with a suitable complex multiplication by an imaginary quadratic number field. These abelian varieties are said to be of Weil type and these Hodge classes are known as Weil classes. We prove that the Weil classes are algebraic for all abelian sixfold of Weil type of discriminant -1, for all imaginary quadratic number fields. The algebraicity of the Weil classes follows for all abelian fourfolds of Weil type (for all discriminants and all imaginary quadratic number fields), by a degeneration argument of C. Schoen. The Hodge Conjecture for abelian fourfolds is known to follow from the above result.
format Preprint
id arxiv_https___arxiv_org_abs_2502_03415
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Cycles on abelian 2n-folds of Weil type from secant sheaves on abelian n-folds
Markman, Eyal
Algebraic Geometry
A. Weil identified a 2-dimensional space of rational classes of Hodge type (n,n) in the middle cohomology of every 2n-dimensional abelian variety with a suitable complex multiplication by an imaginary quadratic number field. These abelian varieties are said to be of Weil type and these Hodge classes are known as Weil classes. We prove that the Weil classes are algebraic for all abelian sixfold of Weil type of discriminant -1, for all imaginary quadratic number fields. The algebraicity of the Weil classes follows for all abelian fourfolds of Weil type (for all discriminants and all imaginary quadratic number fields), by a degeneration argument of C. Schoen. The Hodge Conjecture for abelian fourfolds is known to follow from the above result.
title Cycles on abelian 2n-folds of Weil type from secant sheaves on abelian n-folds
topic Algebraic Geometry
url https://arxiv.org/abs/2502.03415