English

A remark on the intersection of plane curves

Algebraic Geometry 2019-01-08 v4

Abstract

Let DD be a very general curve of degree d=2ϵd=2\ell-\epsilon in P2\mathbb{P}^2, with ϵ{0,1}\epsilon\in \{0,1\}. Let ΓP2\Gamma \subset \mathbb{P}^2 be an integral curve of geometric genus gg and degree mm, ΓD\Gamma \neq D, and let ν:CΓ\nu: C\to \Gamma be the normalization. Let δ\delta be the degree of the \emph{reduction modulo 2} of the divisor ν(D)\nu^*(D) of CC. In this paper we prove the inequality 4g+δm(d8+2ϵ)+54g+\delta\geqslant m(d-8+2\epsilon)+5. We compare this with similar inequalities due to Geng Xu and Xi Chen. Besides, we provide a brief account on genera of subvarieties in projective hypersurfaces.

Keywords

Cite

@article{arxiv.1704.00320,
  title  = {A remark on the intersection of plane curves},
  author = {C. Ciliberto and F. Flamini and M. Zaidenberg},
  journal= {arXiv preprint arXiv:1704.00320},
  year   = {2019}
}

Comments

to appear in Cont. Math. ("Selim Krein Centennial"), pp. 1-19. Collaboration has benefitted by "MIUR Excellence Department Project" Dep. of Mathematics, University of Rome Tor Vergata, CUP E83C18000100006, grant 346300 for "IMPAN" from the "Simons Foundation"(code: BCSim-2018-s09), funds "Mission Sustainability 2017 - Fam Curves" CUP E81-18000100005 (Tor Vergata)