English

Special components of Noether-Lefschetz loci

Algebraic Geometry 2021-09-17 v1 Algebraic Topology Complex Variables

Abstract

We take a sum C1+rC2, rQC_1+r C_2,\ r\in\mathbb Q of a line C1C_1 and a complete intersection curve C2C_2 of type (3,3)(3,3) inside a smooth surface of degree 88 and with C1C2=C_1\cap C_2=\emptyset. We gather evidences to the fact that for all except a finite number of rr, the Noether-Lefschetz loci attached to the cohomology classes of C1+rC2C_1+ r C_2 are distinct 3131 codimensional subvarieties intersecting each other in a 3232 codimensional subvariety of the ambient space. The maximum codimension for components of the Noether-Lefschetz locus in this case is 3535, and hence, we provide a conjectural description of a counterexample to a conjecture of J. Harris. The methods used in this paper also produce in a rigorous way an infinite number of general components passing through the point representing the Fermat surface of degree 9\leq 9, and many non-reduced components for such degrees.

Keywords

Cite

@article{arxiv.1908.04117,
  title  = {Special components of Noether-Lefschetz loci},
  author = {Hossein Movasati},
  journal= {arXiv preprint arXiv:1908.04117},
  year   = {2021}
}
R2 v1 2026-06-23T10:45:07.447Z