Cuspidal discrete series for semisimple symmetric spaces
  We propose a notion of cusp forms on semisimple symmetric spaces. We then study the real hyperbolic spaces in detail, and show that there exists both cuspidal and non-cuspidal discrete series. In particular, we show that all the spherical discrete series are non-cuspidal. 
Nils Byrial Andersen, Mogens Flensted-Jensen and Henrik Schlichtkrull
math.RT