Newforms and the field of definition of an automorphic representation

Brooks Roberts
Department of Mathematics, University of Idaho

Abstract: Certain Hilbert spaces, called automorphic representations, are basic objects in contemporary number theory. An automorphic representation is a representation of a classical linear group on a Hilbert space which satisfies a very strong symmetry condition with respect to the integral points of the group. Though they generalize Dirichlet characters, automorphic representations are typically infinite dimensional. However, it may happen that an automorphic representation contains a canonical vector, called a newform, which encapsulates the number theoretic information hidden in the automorphic representation. This is true for automorphic representations of the symmetry group of the classical upper half plane. In this talk we will discuss joint work with Ralf Schmidt which indicates that automorphic representations of the symmetry group of the Siegel upper half space also admit newforms.