English

Cyclic covers: Hodge theory and categorical Torelli theorems

Algebraic Geometry 2023-12-11 v2

Abstract

Let YY admit a rectangular Lefschetz decomposition of its derived category, and consider a cyclic cover XYX\to Y ramified over a divisor ZZ. In a setting not considered by Kuznetsov and Perry, we define a subcategory AZ\mathcal{A}_Z of the equivariant derived category of XX which contains, rather than is contained in, Db(Z)\mathrm{D}^{\mathrm{b}}(Z). We then show that the equivariant category of the Kuznetsov component of XX is decomposed into copies of AZ\mathcal{A}_Z. As an application, we relate AZ\mathcal{A}_Z with the cohomology of ZZ under some numerical assumptions. In particular, we obtain categorical Torelli theorems for the lowest degree prime Fano threefolds of index 1 and 2.

Keywords

Cite

@article{arxiv.2310.13651,
  title  = {Cyclic covers: Hodge theory and categorical Torelli theorems},
  author = {Hannah Dell and Augustinas Jacovskis and Franco Rota},
  journal= {arXiv preprint arXiv:2310.13651},
  year   = {2023}
}

Comments

19 pages. Added a categorical Torelli theorem for prime Fano threefolds of index 2 and degree 1. Slightly weakened the generality assumptions. Other minor changes. Comments welcome!