Arithmetic monodromy of hyper-Kähler varieties over p-adic fields
アブストラクト
For a hyper-Kähler variety X over a p-adic field, I will explain the relation between the p-adic and $\ell$-adic monodromy operators and the Looijenga-Lunts-Verbitsky Lie algebras. Using this, I will give a formula for the nilpotency indices of these monodromy operators on higher-degree cohomology groups of X, assuming that X belongs to one of the four known deformation types. The formula is expressed in terms of the type of degeneration of the Kuga-Satake abelian variety associated with X. This can be viewed as an arithmetic analogue of Nagai’s conjecture for degenerations of complex hyper-Kähler manifolds over a disk. As an application, I will discuss some $\ell$-independence results (including $\ell=p$) for the characteristic polynomials of the Frobenius operators. This is a joint work with Tetsushi Ito, Teruhisa Koshikawa, Teppei Takamatsu, and Haitao Zou.