English

On non-proper intersections and local intersection numbers

Complex Variables 2021-06-21 v2 Algebraic Geometry

Abstract

Given pure-dimensional (generalized) cycles μ1\mu_1 and μ2\mu_2 on a complex manifold YY we introduce a product μ1Yμ2\mu_1\diamond_{Y} \mu_2 that is a generalized cycle whose multiplicities at each point are the local intersection numbers at the point. % If YY is projective, then given a very ample line bundle LYL\to Y we define a product μ1\blμ2\mu_1\bl \mu_2 whose multiplicities at each point also coincide with the local intersection numbers. In addition, provided that μ1\mu_1 and μ2\mu_2 are effective, this product satisfies a B\'ezout inequality. If i ⁣:Y\PkNi\colon Y\to \Pk^N is an embedding such that i\Ok(1)=Li^*\Ok(1)=L, then μ1\blμ2\mu_1\bl \mu_2 can be expressed as a mean value of St\"uckrad-Vogel cycles on \PkN\Pk^N. There are quite explicit relations between \diY\di_Y and \bl\bl.

Keywords

Cite

@article{arxiv.2003.06180,
  title  = {On non-proper intersections and local intersection numbers},
  author = {Mats Andersson and Håkan Samuelsson Kalm and Elizabeth Wulcan},
  journal= {arXiv preprint arXiv:2003.06180},
  year   = {2021}
}
R2 v1 2026-06-23T14:13:43.903Z