UNIPOTENT ALMOST CHARACTERS OF SIMPLE p-ADIC GROUPS
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0.1. Let G be a simple adjoint algebraic group defined and split over the finite field F[subscript q]. Let K[subscript 0] = [bar over F][subscript q]((ǫ)), K =[bar over F][subscript q]((ǫ)). We are interested in the characters of the standard representations (in the sense of Langlands) of G(K[subscript 0]) corresponding to the (irreducible) unipotent representations ([L6]) of G(K[subscript 0]), restricted to the set G(K[subscript 0])[subscript rsc] = G(K)[subscript rsc] ∩ G(K[subscript 0]) where G(K)[subscript rsc] is the intersection of the set G(K)[subcript rs] of regular semisimple elements in G(K) with the set G(K)[subscript c] of compact elements in G(K) (that is, elements which normalize some Iwahori subgroup of G(K)); we call these restrictions the unipotent characters of G(K[subscript 0]). We hope that the unipotent characters (or some small linear combination of them) have a geometric meaning in the same way as the characters of (irreducible) unipotent representations of G(F[subscript q]) can be expressed in terms of character sheaves on G. Thus we are seeking some geometric objects on G(K)[subscript c] on which the Frobenius map acts and from which the unipotent characters can be recovered.
DepartmentMassachusetts Institute of Technology. Department of Mathematics
Société mathématique de France
Lusztig, Geoge. "Unipotent almost characters of simple p-adic groups." Astérisque, 370, 2015, pp. 243-267