Date: 
June 12, 2008, 15:30  17:00 
Place: 
IPMU PrefabB, Kashiwa Campus of the University of Tokyo 
Speaker: 
Shushi Harashita (IPMU) 
Title: 
Generic Newton polygons of EkedahlOort strata in the moduli space of
abelian varieties. 
Abstract: 
We study the moduli space of principally polarized abelian
varieties in
positive characteristic. The moduli space has two main stratifications,
called Newton polygon (NP) stratification and EkedahlOort (EO) stratification.
It is considered very important in arithmetic geometry to clarify the
singularities of NP strata. As a first step it would be natural to investigate
the intersections of NP strata and EO strata. In this talk I will introduce
an algorithm determining the Newton polygon of any generic point of
each EO stratum,
which is closely related to Oort's conjecture on the intersections of
NP strata and EO strata.
I will also show that certain unions of EO strata contained in the
supersingular locus
can be beautifully described in terms of DeligneLusztig varieties.
