On the cohomology of congruence subgroups of GL_3 over imaginary quadratic fields

Abstract: 

The complex group cohomology of congruence subgroups provides a geometric incarnation of certain spaces of automorphic forms.  In this joint work with Paul Gunnells and Mark McConnell, we investigate the cohomology for congruence subgroups of GL_3 over the Eisenstein integers as a Hecke module.  This represents the first attempt at such computations.  In this talk, I will discuss the computational framework as well as the results of the computation.  In our results we observe a variety of phenomena, including cohomology classes that apparently correspond to nonselfdual cuspforms.