Euler-Poincaré formulae for positive depth Bernstein projectors

Abstract

Work of Bezrukavnikov-Kazhdan-Varshavsky uses an equivariant system of trivial idempotents of Moy-Prasad groups to obtain an Euler-Poincaré formula for the r-depth Bernstein projector. Barbasch-Ciubotaru-Moy use depth-zero cuspidal representations of parahoric subgroups to decompose the Euler-Poincaré presentation of the depth-zero projector. For positive depth $r$, we establish a decomposition of the Euler-Poincaré presentation of the r-depth Bernstein projector based on a notion of associate classes of cuspidal pairs for Moy-Prasad quotients. We apply these new Euler-Poincaré presentations to the obtain decompositions of the resolutions of Schneider-Stuhler and Bestvina-Savin.

36 pages, 2 figures