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KK-theoretic duality for proper twisted actions

Siegfried Echterhoff·Heath Emerson·Hyun Jeong Kim
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Abstract

Let the discrete group G act properly and isometrically on the Riemannian manifold X. Let C_0(X, δ) be the section algebra of a smooth locally trivial G-equivariant bundle of elementary C*-algebras representing an element δof the Brauer group Br_G(X). Then C_0(X,δ^{-1}) x G is KK-theoretically Poincare dual to (C_0(X,δ)\otimes_{C_0(X)} C_τ(X)) xG, where δ^{-1} is the inverse of δin the Brauer group. We deduce this from a strengthening of Kasparov's duality theorem RKK^G(X; A,B) \cong KK^G(C_τ(X)\otimes A, B). As applications we also obtain a version of the above Poincare duality with X replaced by a compact G-manifold M and for twisted group algebras C*(G,ω) if G satisfies some additional properties related to the Dirac-dual Dirac method for the Baum-Connes conjecture.

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Siegfried Echterhoff, Heath Emerson, Hyun Jeong Kim. 2007-08-10. KK-theoretic duality for proper twisted actions. https://arxiv.org/abs/math/0610044

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