Matrix coefficients of cohomologically induced representations

Abstract

Let $G$ be a connected semisimple Lie group with a finite center, with a maximal compact subgroup $K$. There are two general methods to construct representations of $G$, namely, ordinary parabolic induction and cohomological parabolic induction. We define Eisenstein integrals relative to cohomological inductions which generalize Flensted-Jensen's fundamental functions for discrete series. They are analogous to Harish-Chandra's Eisenstein integrals related to ordinary inductions. We introduce the notion of Li positivity of a $K$ type in a representation of $G$ which is extremely useful in the study of branching laws. As an application of our integral, we show that the minimal $K$ types of many interesting representations are Li positive. These include all irreducible unitary representations with nonzero cohomology.