Chern Simons invariants in $KK$ theory

Abstract

For a unitary representation of the fundamental group of a compact smooth manifold, Atiyah, Patodi, Singer defined the so called alpha-invariant of the representation using Chern-Simons invariants. In this article using traces on C*-algebras, we define intrinsically(i.e without using Chern character) an element in KK-theory with real coefficients theory whose pullback by the representation is the alpha-invariant.