Class groups and general linear group cohomology for a ring of algebraic integers

Class Groups and General Linear Group Cohomology for a Ring of Algebraic Integers

Suppose that F is a number field, with ring of integers OF . Let ` denote an odd prime and let R = OF [1/`]. In [3], the author and W.Dwyer gave an explicit conjectural computation of the mod ` cohomology of the infinite general linear group GLR. Here is the quickest and simplest statement of the conjecture (all homology and cohomology groups have Z/` coefficients): let U denote the infinite un...

The Coherent Cohomology Ring of an Algebraic Group

Let G be a group scheme of finite type over a field, and consider the cohomology ring H∗(G) with coefficients in the structure sheaf. We show that H∗(G) is a free module of finite rank over its component of degree 0, and is the exterior algebra of its component of degree 1. When G is connected, we determine the Hopf algebra structure of H∗(G).

Equivariant Cohomology in Algebraic Geometry Lecture Fourteen: General Lie Groups

for nonnegative integers nβα. Each root β corresponds to a unipotent subgroup Uβ of G, whose Lie algebra is gβ. There is an isomorphism of the additive Lie groupGa ∼= C with Uβ; this is T -equivariant, with multiplication by β(t) on C corresponding to conjugation by t on Uβ (u 7→ tut −1). The product of the groups Uβ for β ∈ R+ forms a unipotent group U , isomorphic to C , with N = #R+, and B =...

Detecting Rational Cohomology of Algebraic Groups

Let G be a connected, semisimple algebraic group defined over an algebraically closed field k of positive characteristic p. Assume that G is defined and split over the prime field k0 = GF (p), and for q = p , let G(q) be the subgroup of GF (g)-rational points. Let V be a rational G-module, and, for a non-negative integer r, let V(r) be the rational G-module obtained by 'twisting' the original G...

The Cohomology of a Coxeter Group with Group Ring Coefficients