| Résume | The Siegel moduli space of principally polarized abelian varieties has a natural decomposition according to the isogeny class of the universal p-divisible group, called the Newton stratification. Generically on each non-closed stratum, the universal principally polarized abelian variety does not have any automorphisms except for 1 and -1. We explain how to prove a conjecture of Oort stating the same also for the closed (or supersingular) Newton stratum, except for those primes p and dimensions where the conjecture is already known to fail. |
