arXiv subjects
Publications and source records attributed to Stephan Neupert.
For arbitrary reductive groups $G$ defined over a finite field, we decompose Newton strata in the special fiber of moduli spaces of global $G$-shtukas into a product of Rapoport-Zink spaces and Igusa varieties. This allows us to compare the $\ell$-adic cohomology of these spaces together with the various actions on them.
For connected reductive groups G over a finite extension F of Q_p and L the maximal unramified extension of F we study the sets H_{μ, N}(G) of elements b in G(L) with given Hodge points of (bσ), (bσ)^2, ..., (bσ)^N. We explain the relationship to stratifications of some moduli scheme of abelian varieties defined by Goren and Oort respectively Andreatta and Goren. We show that for sufficiently large N the Newton point is constant on the sets H_{μ, N}(G) and compute such N for certain classes of groups.