Calabi-Yau threefolds over finite fields and torsion in cohomologies

Abstract

We study various examples of Calabi-Yau threefolds over finite fields. In particular, we provide a counterexample to a conjecture of K. Joshi on lifting Calabi-Yau threefolds to characteristic zero. We also compute the p-adic cohomologies of some Calabi-Yau threefolds constructed by Cynk-van Straten which have remarkable arithmetic properties, as well as those of the Hirokado threefold. These examples and computations answer some outstanding questions of B. Bhatt, T. Ekedahl, van der Geer-Katsura and Patakfalvi-Zdanowicz, and shed new light on the Beauville-Bogomolov decomposition in positive characteristic. Our tools include p-adic Hodge theory as well as classical algebraic topology. We also give potential examples showing that Hodge numbers of threefolds in positive characteristic are not derived invariants, contrary to the case of characteristic zero.

arXiv commentComments welcome!

References in corpus (8)

• Chiral Rings Do Not Suffice: N=(2,2) Theories with Nonzero Fundamental Group
• Calabi-Yau Duals of Torus Orientifolds
• On non-liftable Calabi-Yau threefolds
• The Brauer group is not a derived invariant
• The Spectral Construction for a (1,8)-Polarized Family of Abelian Varieties
• Abelian Fibrations, String Junctions, and Flux/Geometry Duality
• Calabi-Yau threefolds in positive characteristic
• An Example of non-simply connected non-liftable Calabi-Yau 3-fold in positive characteristic

Cited by in corpus (1)

• Hodge numbers are not derived invariants in positive characteristic