English

Complex vs etale Abel Jacobi map and algebraicity of the zero locus of etale normal functions

Algebraic Geometry 2023-08-03 v9

Abstract

We prove, using pp-adic Hodge theory for open algebraic varieties, that for a smooth projective variety over a subfield kCk\subset\mathbb C which is of finite type over Q\mathbb Q, the complex abel jacobi map vanishes if the etale abel jacobi map vanishes. This implies that for a smooth projective morphism f:XSf:X\to S of smooth complex algebraic varieties over kCk\subset\mathbb C which is of finite type over Q\mathbb Q and ZZd(X,n)f,=0Z\in\mathcal Z^d(X,n)^{f,\partial=0} an algebraic cycle flat over SS whose cohomology class vanishes on fibers, the zero locus of the etale normal function associated to ZZ is contained in the zero locus of the complex normal function associated to ZZ. From the work of Saito or Charles, we deduce that the zero locus of the complex normal function associated to ZZ is defined over the algebraic closure kˉ\bar k of kk if the zero locus of the etale normal function associated to ZZ is not empty. We also prove an algebraicity result for the zero locus of an etale normal function associated to an algebraic cycle over a field of finite type over Q\mathbb Q. By the way, for a smooth morphism f:XSf:X\to S of smooth algebraic varieties over a field of finite type over Q\mathbb Q, we embed the locus of Hodge-Tate classes of ff inside the locus of Hodge classes of ff.

Keywords

Cite

@article{arxiv.2211.15317,
  title  = {Complex vs etale Abel Jacobi map and algebraicity of the zero locus of etale normal functions},
  author = {Johann Bouali},
  journal= {arXiv preprint arXiv:2211.15317},
  year   = {2023}
}