On the cohomology of GL(N) and adjoint Selmer groups

Abstract

We prove -under certain conditions (local-global compatibility and vanishing of integral cohomology), a generalization of a theorem of Galatius and Venkatesh. We consider the case of GL(N) over a CM field and we relate the localization of penultimate non vanishing cuspidal cohomology group for a locally symmetric space to the Selmer group of the Tate dual of the adjoint representation. More precisely we construct a Hecke-equivariant injection from the divisible group associated to the first fundamental group of a derived deformation ring to the Selmer group of the twisted dual adjoint motive with divisible coefficients and we identify its cokernel as its first Tate-Shafarevich group. Actually, we also construct similar maps for higher homotopy groups with values in exterior powers of Selmer groups, although with less precise control on their kernel and cokernel. We generalize this to Hida families as well.