We study the structure of the moduli space of principally polarized abelian varieties in characteristic p. In this paper we determine the configuration of the central streams in the moduli space. As a corollary of our proof we obtain a new proof of the dimension formula of the central streams.
Shushi Harashita. "Configuration of the Central Streams in the Moduli of Abelian Varieties." Asian J. Math. 13 (2) 215 - 250, June 2009.