2014/11/18 by Li, Jinghao
#Algebraic Geometry (math.AG) #FOS: Mathematics
paper · doi:10.48550/arxiv.1411.4699
For an Fn-crystal \mathfrak C over a reduced locally Noetherian \mathbb Fp-scheme S, Vasiu first obtained the purity of the Newton polygon strata of S defined by \mathfrak C. Deligne later obtained the purity of the p-rank strata of S defined by \mathfrak C. We prove a stronger result that for every fixed point P0 in the xy-coordinate plane, the reduced locally closed subscheme SP0=\s∈ S| NP(\mathfrak Cs) has P0 as a break point\ of S is pure in S (A weaker result was known for the weak purity of Sp0).