Sug Woo Shin : Non-emptiness of Newton strata

Posted by Izzet Coskun , part of the Algebraic Geometry Seminar.

At

Feb. 6, 2013, 4 p.m.

In

SEO 427

Abstract

A Newton stratum for Shimura varieties (certain moduli spaces of abelian varieties with extra data in characteristic p) is the locus where the p-divisible groups belong to a fixed isogeny class. In case the moduli problem is defined by unitary or symplectic data (which are unramified), Newton strata are known to be nonempty whenever expected by Vasiu and Viehmann-Wedhorn based on earlier work by many, and also recently by Kret. I will explain a different approach to prove the result in the unramified case via Honda-Tate theory and Galois cohomology.