Zonal Functions for the Unitary Groups and Applications to Hermitian Lattices

We study the decomposition of the space L²(Sⁿ⁻¹) under the actions of the complex and quaternionic unitary groups. We give an explicit basis for the space of zonal functions, which in the second case takes account of the action of the group of quaternions of norm 1. We derive applications to hermitian lattices.