Steinberg representations for groups of parahoric types: the special case

Abstract

In this paper, we define and study a kind of Steinberg representation for linear algebraic groups of a particular kind, called groups of parahoric type, defined overa finite field; in particular, when G is the group of F-points of a connected reductive quasisplit group defined over F which splits over an unramified extension of F, the quotients of parahoric subgroups of G by their congruence subgroups are groups of parahoric type. In particular, under certain conditions on the residual characteristic p of F, we determine the irreducible factors of the Steinberg representation of a group of parahoric type associated to a pseudo-Borel subgroup of this group in the special case, that is when this group os a quotient of a maximal special parahoric subgroup of G.