English

GIT stable cubic threefolds and certain fourfolds of $K3^{[2]}$-type

Algebraic Geometry 2025-03-27 v2

Abstract

We study the behaviour on some nodal hyperplanes of the isomorphism, described in a paper of 2019 by Boissi\`ere, Camere and Sarti, between the moduli space of smooth cubic threefolds and the moduli space of hyperk\"ahler fourfolds of K3[2]K3^{[2]}-type with a non-symplectic automorphism of order three, whose invariant lattice has rank one and is generated by a class of square 6; along those hyperplanes the automorphism degenerates by jumping to another family. We generalize their result to singular nodal cubic threefolds having one singularity of type AiA_i for i=2,3,4i=2, 3, 4 providing birational maps between the loci of cubic threefolds where a generic element has an isolated singularity of the types AiA_i and some moduli spaces of hyperk\"ahler fourfolds of K3[2]K3^{[2]}-type with non-symplectic automorphism of order three belonging to different families. In order to treat the A2A_2 case, we introduce the notion of K\"ahler cone sections of KK-type generalizing the definition of KK-general polarized hyperk\"ahler manifolds.

Keywords

Cite

@article{arxiv.2301.11149,
  title  = {GIT stable cubic threefolds and certain fourfolds of $K3^{[2]}$-type},
  author = {Lucas Li Bassi},
  journal= {arXiv preprint arXiv:2301.11149},
  year   = {2025}
}

Comments

Second version, minor changes

R2 v1 2026-06-28T08:21:37.109Z