Hochs, P.Wang, H.2020-10-282020-10-282019Annals of K-Theory, 2019; 4(2):185-2092379-16832379-1691http://hdl.handle.net/2440/128691Let G be a semisimple Lie group with discrete series. We use maps K₀(C∗rG)→C defined by orbital integrals to recover group theoretic information about G, including information contained in K-theory classes not associated to the discrete series. An important tool is a fixed point formula for equivariant indices obtained by the authors in an earlier paper. Applications include a tool to distinguish classes in K₀(C∗rG), the (known) injectivity of Dirac induction, versions of Selberg’s principle in K-theory and for matrix coefficients of the discrete series, a Tannaka-type duality, and a way to extract characters of representations from K-theory. Finally, we obtain a continuity property near the identity element of G of families of maps K₀(C∗rG)→C, parametrised by semisimple elements of G, defined by stable orbital integrals. This implies a continuity property for L-packets of discrete series characters, which in turn can be used to deduce a (well-known) expression for formal degrees of discrete series representations from Harish-Chandra’s character formula.en© 2019 Mathematical Sciences PublishersK-theory of group C*-algebras; orbital integral; equivariant index; semisimple Lie group; Connes–Kasparov conjectureOrbital integrals and K-theory classesJournal article100002793210.2140/akt.2019.4.185551784Hochs, P. [0000-0001-9232-2936]