2023/09/07 by Chmiel, Tymoteusz, Oczko, Marcin
#Algebraic Geometry (math.AG) #FOS: Mathematics
paper · doi:10.48550/arxiv.2309.04008
For any prime p>5 we construct a Calabi-Yau threefold X defined over a finite extension K of ℚp such that every model of X over SpecOK has singular special fiber, yet the Galois action on the ℓ-adic cohomology group H3_\acuteet(X,ℚ_ℓ) is unramified for ℓ≠ p and crystalline for ℓ=p. This provides a counterexample to the analogue of the Néron-Ogg-Shafarevich criterion for three-dimensional Calabi-Yau manifolds.