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Traces for star products on the dual of a Lie algebra

Pierre Bieliavsky·Martin Bordemann·Simone Gutt·Stefan Waldmann
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Abstract

In this paper, we describe all traces for the BCH star-product on the dual of a Lie algebra. First we show by an elementary argument that the BCH as well as the Kontsevich star-product are strongly closed if and only if the Lie algebra is unimodular. In a next step we show that the traces of the BCH star-product are given by the $\ad$-invariant functionals. Particular examples are the integration over coadjoint orbits. We show that for a compact Lie group and a regular orbit one can even achieve that this integration becomes a positive trace functional. In this case we explicitly describe the corresponding GNS representation. Finally we discuss how invariant deformations on a group can be used to induce deformations of spaces where the group acts on.

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Pierre Bieliavsky, Martin Bordemann, Simone Gutt, Stefan Waldmann. 2002-03-19. Traces for star products on the dual of a Lie algebra. https://doi.org/10.1142/s0129055x03001643

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