Journal of Noncommutative Geometry

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Volume 12, Issue 1, 2018, pp. 157–193
DOI: 10.4171/JNCG/273

Published online: 2018-03-23

An equivariant index for proper actions II: Properties and applications

Peter Hochs and Yanli Song[1]

(1) Washington University, St. Louis, USA

In the first part of this series, we defined an equivariant index without assuming the group acting or the orbit space of the action to be compact. This allowed us to generalise an index of deformed Dirac operators, defined for compact groups by Braverman. In this paper, we investigate properties and applications of this index. We prove that it has an induction property that can be used to deduce various other properties of the index. In the case of compact orbit spaces, the index is a special case of Kasparov’s index of transversally elliptic operators. In that case, we show how it is related to the analytic assembly map from the Baum–Connes conjecture, and an index used by Mathai and Zhang. In the case of noncompact orbit spaces, we use the index to define a notion of $K$-homological Dirac induction, and show that, under conditions, it satisfies the quantisation commutes with reduction principle.

Keywords: Equivariant index, proper group action, analytic $K$-homology

Hochs Peter, Song Yanli: An equivariant index for proper actions II: Properties and applications. J. Noncommut. Geom. 12 (2018), 157-193. doi: 10.4171/JNCG/273