Finite descent obstruction for Hilbert modular varieties

Abstract

Let $S$ be a finite set of primes. We prove that a form of finite Galois descent obstruction is the only obstruction to the existence of ${\mathbb{Z}}_S$-points on integral models of Hilbert modular varieties, extending a result of D.Helm and F.Voloch about modular curves. Let $L$ be a totally real field. Under (a special case of) the absolute Hodge conjecture and a weak Serre's conjecture for mod $\ell$ representations of the absolute Galois group of $L$, we prove that the same holds also for the ${\mathcal{O}}_{L,S}$-points.

To appear in Canadian Mathematical Bulletin