English

Deformations of hypersurfaces with non-constant Alexander polynomial

Algebraic Geometry 2023-10-10 v3

Abstract

Let X be an irreducible hypersurface in Pn\mathbb{P}^n of degree d3d\geq 3 with only isolated semi-weighted homogeneous singularities, such that exp(2πik)exp(\frac{2\pi i}{k}) is a zero of the Alexander polynomial. Then we show that the equianalytic deformation space of XX is not TT-smooth except for a finite list of triples (n,d,k)(n,d,k). This result captures the very classical examples by B. Segre of families of degree 6m6m plane curves with 6m26m^2, 7m27m^2, 8m28m^2 and 9m29m^2 cusps, where m3m\geq 3. Moreover, we argue that many of the hypersurfaces with non-trivial Alexander polynomial are limits of constructions of hypersurfaces with not TT-smooth deformation spaces. In many instances this description can be used to construct Alexander-equivalent Zariski pairs.

Keywords

Cite

@article{arxiv.2107.10604,
  title  = {Deformations of hypersurfaces with non-constant Alexander polynomial},
  author = {Remke Kloosterman},
  journal= {arXiv preprint arXiv:2107.10604},
  year   = {2023}
}

Comments

Compared to v1: The main theorem has been slightly improved. Several minor changes. Section 2 rewritten Compared to v2: minor changes