Analytic Pontryagin Duality

Abstract

Let X be a smooth compact manifold. We propose a geometric model for the group K⁰(X,R/Z): We study a well-defined and non-degenerate analytic duality pairing between K⁰(X,R/Z) and its Pontryagin dual group, the Baum-Douglas geometric K-homology K₀(X); whose pairing formula comprises of an analytic term involving the Dai-Zhang eta-invariant associated to a twisted Dirac-type operator and a topological term involving a differential form and some characteristic forms. This yields a robust R/Z-valued invariant. We also study two special cases of the analytic pairing of this form in the cohomology groups H¹(X,R/Z) and H²(X,R/Z):