English

Varieties of Picard rank one as components of ample divisors

Algebraic Geometry 2014-02-05 v1

Abstract

Let V\mathcal{V} be an integral normal complex projective variety of dimension n3n\geq 3 and denote by L\mathcal{L} an ample line bundle on V\mathcal{V}. By imposing that the linear system L|\mathcal{L}| contains an element A=A1+...+Ar,r1A=A_{1}+...+A_{r}, r\geq 1, where all the AiA_{i}'s are distinct effective Cartier divisors with Pic(Ai)=Z(A_i)=\mathbb{Z}, we show that such a V\mathcal{V} is as special as the components AiA_i of ALA\in |\mathcal{L}|. After making a list of some consequences about the positivity of the components AiA_i, we characterize pairs (V,L)(\mathcal{V}, \mathcal{L}) as above when either A1Pn1A_1\cong\mathbb{P}^{n-1} and Pic(Aj)=Z(A_j)=\mathbb{Z} for j=2,...,r,j=2,...,r, or V\mathcal{V} is smooth and each AiA_i is a variety of small degree with respect to [Hi]Ai[H_i]_{A_i}, where [Hi]Ai[H_i]_{A_i} is the restriction to AiA_i of a suitable line bundle HiH_i on V\mathcal{V}.

Keywords

Cite

@article{arxiv.1402.0839,
  title  = {Varieties of Picard rank one as components of ample divisors},
  author = {Andrea Luigi Tironi},
  journal= {arXiv preprint arXiv:1402.0839},
  year   = {2014}
}

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15 pages LaTeX