An asymptotic description of the Noether-Lefschetz components in toric varieties (1905.01570v3)

Abstract: We extend the definition of Noether-Leschetz components to quasi-smooth hypersurfaces in a projective simplicial toric variety of dimension 2k+1, and prove that asymptotically the components whose codimension is upper bounded by a suitable effective constant correspond to hypersurfaces containing a small degree k-dimensional subvariety. As a corollary we get an asymptotic characterization of the components with small codimension, generalizing Otwinowska's work for odd-dimensional projective spaces and Green and Voisin's for projective 3-space. Some tools that are developed in this paper are a generalization of Macaulay theorem forprojective irreducible varieties with zero irregularity, and an extension of the notion of Gorenstein ideal to Cox rings of projective simplicial toric varieties.