Journal Home Page Cumulative Index List of all Volumes Complete Contentsof this Volume Previous Article Journal of Lie Theory 30 (2020), No. 3, 715--765Copyright Heldermann Verlag 2020 Irreducible Characters and Semisimple Coadjoint Orbits Benjamin Harris U.S.A. benjaminlharris@outlook.com Yoshiki Oshima Dept. of Pure and Applied Mathematics, Grad. School of Information Science and Technology, Osaka University, Suita Osaka 565-0871, Japan oshima@ist.osaka-u.ac.jp [Abstract-pdf] When $G_{\mathbb{R}}$ is a real, linear algebraic group, the orbit method predicts that nearly all of the unitary dual of $G_{\mathbb{R}}$ consists of representations naturally associated to orbital parameters $(\mathcal{O},\Gamma)$. If $G_{\mathbb{R}}$ is a real, reductive group and $\mathcal{O}$ is a semisimple coadjoint orbit, the corresponding unitary representation $\pi(\mathcal{O}, \Gamma)$ may be constructed utilizing Vogan and Zuckerman's cohomological induction together with Mackey's real parabolic induction. In this article, we give a geometric character formula for such representations $\pi(\mathcal{O},\Gamma)$. Special cases of this formula were previously obtained by Harish-Chandra and Kirillov when $G_{\mathbb{R}}$ is compact and by Rossmann and Duflo when $\pi(\mathcal{O},\Gamma)$ is tempered. Keywords: Semisimple orbit, coadjoint orbit, orbit method, Kirillov's character formula, cohomological induction, parabolic induction, reductive group. MSC: 22E46. [ Fulltext-pdf  (336  KB)] for subscribers only.