English

Planes in cubic fourfolds

Algebraic Geometry 2024-08-20 v2

Abstract

We show that the maximal number of planes in a complex smooth cubic fourfold in P5{\mathbb P}^5 is 405405, realized by the Fermat cubic only; the maximal number of real planes in a real smooth cubic fourfold is 357357, realized by the so-called Clebsch--Segre cubic. Altogether, there are but three (up to projective equivalence) cubics with more than 350350 planes.

Keywords

Cite

@article{arxiv.2105.13951,
  title  = {Planes in cubic fourfolds},
  author = {Alex Degtyarev and Ilia Itenberg and John Christian Ottem},
  journal= {arXiv preprint arXiv:2105.13951},
  year   = {2024}
}

Comments

Revise version accepted for publication. Newer references and a bound for nodal cubics added

R2 v1 2026-06-24T02:34:46.603Z